While I concur with the concepts already expressed, another one comes to mind. She may be either bipolar or borderline.
Borderline was my thought too, actually, especially if the flip was over a very very short period of time.

I've modeled with the girl before... the thing is that I think I should have seen this coming (I'm rather gullible, and slow on the uptake at times *sigh*) she's recommended photographers to me that she'll vehemently talk down on months later and has sent me random txts that say "I'm so traumatized!" with no follow up even when I txt back asking what has her so traumatized... it's like pulling teeth getting answers from her a lot of the time.
Ding, ding, ding.

Don't beat yourself up for not noticing, sometimes you never know until someone reacts to something in a strange way. Live and learn.

Also... if you're getting death threats, after a consensual play session, it might not be a bad idea to save the texts in case you do need backup in a legal situation. Regardless, it doesn't sound like she's processing very well, and lots and lots of space on your end is the best you can do.