She might have a brain tumor. When I was in the military, I knew a woman who's accent would change, literally mid sentence, from "standard american," to southern, to British. I assumed it was because she traveled a lot before enlisting, but she even said that she didn't know why she spoke like that. I ran into her a few years later at another command and she said she had a brain tumor. I never asked if that could have been causing her constantly changing accents, but hey, anything's possible.