She loves Hawaii, but her constituents were loony. I think she felt she could no longer represent them.
That's my take on her as well. She supported the party line for the time she was running on their ticket, but clearly she got sick of the hard-left progressive bullshit. She called them out pretty strongly, and finally split.
I tend to think she's sincere in her more centrist, pro-America stance. Would she make a decent VP pick? Maybe, but I'd like to hear more from her about her positions that are still left-ish, and how she's abandoning them. She'll have to talk about that a lot this year to convince me.
She's still a long way from conservative.