I hesitantly agree with oldlife....with one caveat. While I understand from your post that she is obviously unstable, I'm not sure that the lack of proposal didn't exacerbate the situation or situations. I know you (wisely) would prefer for things to be a little more settled before doing so...but given her already unsteady belief in your love/commitment, it could sound a bit like waiting to have kids when you 'can afford it'. If everyone did that, there would be far fewer kids born and although that might be a good thing, given some of the trauma children go thru because of people who were not ready to be parents, far more great parents became so without having everything perfectly set before getting pregnant.

You know her best, of course, and I also understand your frustration and confusion...but looking at things more from her point of view, she might be afraid she's waiting for your inevitable rejection, rather than proposal. That could add to her already growing anxiety...dragged out anticipation can also feel like slow torture. (I know you're building a house for 'both' of you....but you're perfectly capable of living in it without her, remember. I'm pretty sure she does.)