Beatriz is an officer in the Rebel Army who is the younger sister of Abigail and a villain and playable character in Metal Slug Attack. She is considered the "idol" of the Rebel Army and thus is able to motivate her soldiers to fight better.
Learning that Abigail is struggling in a battle against the Ptolemaic Army's Jupiter Queen, Beatriz and her bodyguards go to assist her sister. Beatriz and Abigail manage to succeed in destroying the Jupiter Queen but right after they do so, Trevor passes by on a motorbike causing Abigail to blush, making Beatriz jealous.
Following an attack on the Rebel base by the Mars People and the Professor's Clone Abby, Beatriz was called in by Abigail and told to the take the Tiger Macha out on a test run. Beatriz fights the Super Devil in the Tiger Macha, but the Super Devil damages the Tiger Macha and wounds Beatriz. Beatriz's bodyguards attempt to get her away, as the objective of her mission had already been completed, but Beatriz refuses as she doesn't want to back away from a fight. However, despite Beatriz's protests, her bodyguards drag her back to the Rebel Army base.
Revival of Intention
Beatriz and Abigail headed to a Rebel base that was currently holding the Frozen Cab. When they got there though, they discovered that it was under attack and that the person behind the attack was none other than Abigail's old mentor Ariadna, who had mysteriously disappeared. Ariadna challenges the two sisters to a fight and becomes impressed with Beatriz, whom she notes analyzes situations to find solutions in a similar way to Abigail. After the battle, Ariadna retreats to return to the Mars People and Abigail requests Beatriz's help in researching information on Ariadna, stating she won't let her memories of her old mentor get in her way.
Encounter of Unknown
Beatriz spotted Clone Abby and Halle as the two were infiltrating a Rebel Army base to get information on the Rebel Army's new Cabrakan Mk III. Beatriz attacks the pair, but Mars Person Pocket calls in the Rugname to assist them and destroy Cabrakan, causing Beatriz to flee.
Try Line 2nd
Beatriz leads the Rebel Army against the Mars People and fights the Professor, determined to beat him to get revenge for her sister. However, the Invaders suddenly intervene in the battle and a Great Mother attacks, causing both sides to turn their attention to it, with Beatriz finding its appearance disgusting.
While her sister Abigail is recovering from injuries she sustained during an attack by the Mars People, Beatriz takes over her duties and oversees the construction of a Rebel snow fort. The Rebels are suddenly attacked by Mars forces and Beatriz is separated from her bodyguards. After about a week after she goes missing, Allen Jr. and Vicky go to look for her. Unbeknownst to them, Beatriz had escaped from the Martians but had gotten amnesia. She later offered shelter to a child lost from a nearby village.
The Back You Can't Reach
While Fio Germi and Roberto Nicola were transporting a weapon for the Regular Army, Beatriz pretended to be a girl by the side of the road in need of help to lure them out so she could steal the weapon. After Roberto stops and tries to help her, Beatriz's bodyguards jump out and apprehend Roberto. Fio soon recognizes the girl as Beatriz, but before she can do anything Beatriz freezes Roberto and the other Regular Army soldiers before making off with the cargo. Fio waits for Roberto to thaw out before reminiscing on how to deal with the situation.
While Fio, Roberto and the others were searching for the stolen cargo, Beatriz ambushes them with falling rocks. After the Regular Army repels Beatriz's attack, Beatriz retreats back to the Rebel Army base but is pursued by the Regular Army. Beatriz ends up leading the Regular Army to the Rebel Army base, causing Allen Jr. to become angered with her. When the Regular Army arrives, Beatriz takes a controller from Allen Jr. and deploys the Cabrakan. When Roberto gets wounded battling it, Beatriz attempts to finish him off but Fio appears with the Thunder Shot and saves him. After the Cabrakan is destroyed, Beatriz laments that she will die without seeing her sister again but is brought back to reality by Allen Jr., who forcefully drags her away to escape.
The Pharaoh's Treasure
Arriving at the desert ruins, the two notice that Scotia is already there and decide to follow her. Inside, the two find two Mummy Cats (who are startled by Allen Jr. because he is a male) and defeat them. They later find a skeleton which Beatriz guesses is Scotia's father but it turns out to be a Mummy Warrior in disguise After defeating the Mummy Warrior, Beatriz finds the Pharaoh has cursed Allen Jr. and Scotia to sleep. Uneffected by the curse Beatriz demands the Pharaoh hand over the Arabian Tear.
Beatriz and the Pharaoh then fight, with Beatriz ultimately winning. Impressed with her skills and her devotion to her sister, the Pharaoh allows her to take the Arabian Tear. Beatriz then drags Allen Jr. and Scotia back to the surface, while ranting about Allen Jr. being useless. Returning to base, Beatriz gives Morden the jewel, furthering his plans.
Endless Summer Vacation
While Beatriz was vacationing at a beach in the neutral zone with Abigail, she notices that her sister is somewhat off, to which Abigail tells her that something (Trevor) is close. Beatriz later accompanied Abigail and Trevor on their mission to rescue the Mars People who had been kidnapped by Nadia, the Aikawa Sisters and the Ptolemaic girls. The three came to a brook where the Ptolemaic girls were sighted as passing through. Because Beatriz still couldn't swim, Abigail told her to stay behind but Beatriz refused, not trusting her to be alone with Trevor. Beatriz then goes in, but as she cannot swim she is swept away by the current. Trevor then dives in and saves her as a group of monkeys approach the three. Abigail tells the monkeys to stay with Beatriz while she and Trevor dive into the brook to pursue the Ptolemaics.
After Abigail and Trevor saved the Mars People, Beatriz ran back towards her sister on the beach.
In the Secret Ending, Beatriz, exhausted from having to look after Allen Jr., asks Navy to give her an energy booster. Navy asks her if she wants an energy booster that will keep her up for 72 hours or one which will allow her to look after Allen, but Beatriz points to a different one she wants instead. Navy tells her that one has poison in it and Beatriz yells at her, though Navy just returns to her experiments.
We are Mars People Rangers
Beatriz and Abigail both went to check in with Rapid and get an update on the Iron Cab's development. Just then, the two are informed of an attack from the Mars People. Beatriz orders Rapid to go out and fight the Mars People but Rapid refuses, as she isn't a fighter. After the Rebel Army's airstrike against the Mars People fails and their forces are pushed back by the Mars People Tank, Beatriz states she will go out alone to fight the Mars People but Abigail offers to go with her. The two head out to take on the Martian forces and are confronted by Clone Abby, a clone of Abigail created by the Professor. Abigail determines that the Professor must be behind the attack and tells Beatriz to go back, to which Beatriz reluctantly complies. Clone Abby attempts to intercept Beatriz but is stopped by Abigail and the two fight.
While the two are battling, the Mars Rangers attempts to attack the Rebel Army base but Beatriz and her bodyguards ambush them. Mars People Healer attempts to heal them, but Beatriz and her guards fire her freeze gun right at Healer, penetrating the Mars People Tank's shield and directly hitting her. Though Healer is fatally injured, she is rejuvenated by the intervention of Rootmars. Clone Betty and the Martians then show up to assist the Mars Rangers, causing Beatriz to order her men to focus on targeting the Martians. When Clone Abby shows up to assist the Mars People but Abigail doesn't return, Beatriz becomes concerned for her sister and runs off to look for her, leaving her men behind. Clone Abby takes the opportunity to retreat with the rest of the Mars forces back to their base.
While Allen Jr. was looking in Abigail's room wondering where she went, he was yelled at by Beatriz, who was still shaken up by her sister's defeat in the recent attack by the Mars People.
While Abigail pursued her vendetta against the Mars People and the Professor, Beatriz took over for her duties at the Rebel Army. After being informed of increased Ptolemaic Army activity, Beatriz determines whether she should send Abul Abbas to deal with them. A soldier then comes in with some documents for Beatriz to sign. Vicky also appears and states she would like to be in Beatriz's spot. Beatriz refuses and says that only she can be close to Abigail, but allows Vicky to sign the documents for her. Vicky then mentions how Dion might be able to perform his duties unchecked with Abigail gone, causing Beatriz to theorize that Dion might be preventing Abigail from returning, though she quickly shoots it down due to finding it hard to believe Dion could betray Abigail.
Beatriz later walks in on Dion receiving orders from a mysterious figure and asks him if that was Abigail he was talking to, but Dion refuses to tell her anything. Beatriz then warns Dion that she could never forgive him if anything happened to Abigail.
In the Secret Ending, after Abigail defeats the Professor, Beatriz learns she is doing well and wants to see her, only to find she is at the ocean with the Blaze Brigade. After the Blaze Brigade's leader Grazia tells her to get some self-awareness the two get into a scuffle.