I'm sorry about this, what a horrible thing for her to do. I do agree with the point that she probably does not understand the real depth of how you need the dogs and about PTSD itself, as someone who doesn't have it really can't fully understand. My boyfriend really struggles to understand, but he doesn't really. And sometimes he says the complete wrong thing when I know he is trying to be supportive, but it just doesn't work. So, it's hard for our partners to know.
But regardless of that, that is NO reason for her to give an ultimatum like that or be such a downright terrible person to you! As MissAntiSunshine said, even if they were just regular pets and all that, I would think it would be a terrible thing to do, not even taking into account the help these dogs provide you and your condition.
My cat doesn't get along with my boyfriend but if he ever said, "Me or the cat", well I'd take the cat! :) I mean I love my boyfriend to death and all but, you just DON'T say an ultimatum that to someone you love, regardless of the situation. And in this situation with her knowing what the dogs are to you and what their role is, I think it's especially worse.
Also sorry to hear about the ring - that is a complete terrible move on her part. No class at all. That is your property and without a marriage, it rightfully belongs to you. I hope you get it back.
Anyway, it really sucks when our trust is broken like this but not every girl is like this. There's lots of good ones out there.