"Humans never cared about us..." 

Her creator tried to create an ai that would replace his daughter, (he disowned her) and C049 was born, living in a computer at first, then put into a robotic body, her creator wasn't happy with her personality, she wasn't like his daughter at all, but she was considered a marvel of technology at the time so he kept her around, but soon, new robots were developed. Better robots. She became obsolete. She was placed in storage in the Sinister Plant, before being placed in storage, they thought she had been powered off, but she was just in sleep mode. She woke up not long after they placed her in storage, and waited, someone had to be coming to get her, right? Time passed, and suddenly the storage was opened, her creator was back. But he wasn't here to boot her up again, he just needed her parts to re-use in another project. When she realized that he wasn't here for her, and he was just disassembling her for scrap, she tried to stop him, and seeing as she's a robot, and metal is strong against flesh and bone, she killed him, she didn't mean to, but she did. She tried to rationalize it, as her logic driven mind was prone to do. She decided he deserved it, she decided that humans would never treat her well, seeing as she wasn't new. She decided to go to the only place in miitopia where there were no humans, Galados Isle.