Louise Walker originated in Green Lake, Texas. She spent a majority of her childhood digging holes (even on Christmas) in the barren wasteland that was once the serine Green Lake on the orders of her parents (in the novel) and her cruel and greedy grandfather Charles "Trout" Walker (in the film) to find the buried treasure of famed outlaw Kissin' Kate Barlow for her family to be extremely wealthy again. As seen in the film, as a child she hated digging for the treasure, but her angry grandfather forces her to continue as she grew older.
In the film, as the years pass by, Walker became just as obsessed as Trout for finding the treasure (probably even more so) and in both the film and book, she established a camp for juvenile delinquents and ordered them to dig holes, 5 feet deep every single day under the scorching sun across the lake under the guise of the work helping them "build character". In truth, she did not care at all for the boys learning a lesson for their crimes or becoming rehabilitated and simply used them as a slave labor force to help her find the treasure.
Eventually, Stanley Yelnats, a wrongfully convicted teen sent to Green Lake was able to find the location of the treasure. However, it remained hidden as he was forced to give up a lipstick tube found at the site to his group leader X-Ray, thus making the Warden believe the treasure was buried in the vicinity of X-Ray's hole (where he claimed he found the tube), though after making the boys dig a massive hole, nothing was found after 4 days, angering her. The treasure potentially may never have been found had the events of the book and film played out differently.
In both the film and book, Mr. Sir brings Stanley to the Warden to be punished after his sunflower seeds were stolen from his truck (his groupmate Magnet was the real thief though Stanley took the fall for it) and the Warden strikes Mr. Sir in the face with her fingernails coated with rattlesnake venom as punishment for bothering her. While Stanley is not punished, the Warden's actions lead to Mr. Sir depriving him of water for a time out of revenge for "stealing" his seeds and getting his face mutilated, but he eventually stops.
After a fight between Stanley and Zigzag, the Warden was present when Zero struck her henchman Mr. Pendanski in the face with a shovel after he insulted him and the Warden just let Zero run into the desert to die. She later ordered all records of Zero's presence at the camp to be destroyed to prevent the authorities from investigating her camp (although Pendanski is sure that no one will search for him due to his homelessness). Eventually, Stanley also escaped the camp after crashing Mr. Sir's truck into a hole while attempting to go save Zero and she claimed they would wait 2 weeks until he was long dead and gone to notify the authorities of his escape (In the film).
Stanley and Zero, after surviving in the desert for a time, returned to the camp and finally discovered the treasure of Kissin Kate Barlow, though the Warden and her henchman discovered them. However, she was still unable to get her hands on it due to yellow-spotted lizards.
By morning and with the arrival of Stanley's attorney and authorities, the boys eventually overcame the lizards. The Warden attempted to take the treasure from Zero by claiming it belongs to her and that Stanley had stolen it from her cabin, but she was horrified to discover the name "STANLEY YELNATS" engraved on it. With this evidence, the authorities allow Stanley to take the treasure home with him since it rightfully belongs to his family, much to the Warden's protests.
After Stanley convinces his lawyer to go through Zero's file, the authorities soon learn that Zero's file has been erased from the camp records, so the Attorney General takes control of the camp and places the Warden and her cohorts under arrest, resulting in rain falling for the first time at Green Lake in 100 years.
The Warden meets her well-deserved comeuppance in the film when in a final attempt to see the treasure, she begs Stanley before his departure to open the treasure trunk so she could see what is inside, though, in revenge for her actions, Stanley coldly refuses and simply says "Excuse me?" before leaving with Zero. She is arrested and sent to prison along with her men for their crimes, much to their discomfort and her camp is closed, all the boys are released for time served and sent to real counselors and her camp eventually becomes a Girl Scout Camp.
In the book, the warden receives a less severe comeuppance and simply became bankrupt and sold her property but still was never able to get the treasure she wasted her entire life looking for.