I don't know what she was doing in 2012.
I know, however, anecdotally at least that accents don't particularly take long to form. I also know that humans can have more than one accent, and fall into one or another based on context, particularly if they're multilingual. You can even observe a less dramatic version of non multilingual people doing this, ie a person who goes to college in the south, but is from the North switching back and forth. I personally switch back and forth between multiple accents depending on where I am and what language I'm speaking, sometimes on purpose - but often I slip into it just based on spending time with a person, or in a particular place.
Your positing that she's a phony because she's adopting an accent on purpose. I said that may be true, I don't know enough about her life to say that. If you think that's the best explanation based on what you know, I think that's just more power to you.