I'm sorry you feel so disconnected from your sister - and I don't mean that in a "you're the one with the problem" kind of way.

I have no experience with what I'm about to suggest, but is there any chance she is bipolar and is now in a manic/hypomanic episode? I suggest this because you're talking about a total one-eighty. I think

Can you take to her GP or take her to the GP to talk about this, perhaps? He might have some ideas.

Also often insurances have a clause that makes an exception either for serious cases, chronic cases, or different problems. For example you might only be able to be in therapy for two years if you're depressed, but you can do two years for PTSD after that. Or you can do more than two years if you're both depressed and traumatized.