She was played by Ashley Noel.
In the episode, Matilda was transported to an alternate dimension during her latest experiment regarding teleportation; an experiment performed with the help of her fiancee, Nick, her former flame (and Nick's brother), Aaron, and Aaron's girlfriend, Abby. The alternate world is ravaged by war and death, and it was there that Matilda met her doppelganger, Col. Matilda West, the leader of an army. The colonel accused Matilda of being a spy, but both of the ended up transported together with one touch.
With both of them back in the real world, Matilda decided to display Col. West as proof that her experiment works on living organisms. Col. West took a look at Matilda's world and was amazed of how beautiful it looked compared to her world, all the while making a friendly impression on Aaron and Abby--both of whom disliked the real Matilda. She engaged in a sexual encounter with Aaron and later conversed with Abby, but shortly afterwards, both Matildas began to weaken, and it was Nick who concluded that their conditions were due to them being on the same world, meaning that Col. West had to return to her own alternate reality. Before the process took place, Aaron spotted Abby attempting to switch the Matildas so the real one could go and the colonel could remain, and he switched them back.
In the episode's final scenes, however, Abby revealed to Aaron that while she was considering switching the Matildas, she didn't go through with it. This meant that the real Matilda went to the alternate world, while her evil doppelganger remained, and Nick realized this after having sex with who he thought was Matilda--when his lover stated that she didn't want to be in charge anymore. Knowing Matilda's true nature, Nick was shocked to realized that he was with Col. West, and in the end of the episode, the evil Col. West killed Nick, as well as Abby and Aaron. The villainess gave an evil laugh as she walked out of the lab with plans to take over her new dimension.