Wow! It's very hard not to judge.
There are some things that are worth putting up with (low moods, etc.), but this financial stuff is a biggie. And it sound a bit manipulative to me, whether that's her intent or not. Even if her behaviour is a consequence of her PTSD, it's still inconsiderate and financially damaging.
What worries me is that she doesn't seem to consider you at all.
My sufferer, even at his lowest points, will be aware of how his behaviour affects me ("You deserve better!") and be frustrated that he can't be a more stable and supportive partner. That she's asking you for money is a big red flag to me. My man feels bad that I work and he doesn't (because of PTSD), he doesn't expect it.
Best of luck. This woman needs a lot of help, but I'm not sure that it's the healthiest thing for you to me the one to help her. Not if she's not willing to set boundaries and expectations.