I (25/m) need to cut things off in a somewhat unusual situation

Okay, so as for backstory, I (25/m) have been officially with my girlfriend (25/f) for a bit over four months, unofficially involved for some time longer than that. Currently, relationship is long-distance during points in time when I'm a few hundred miles away at grad school. There have been some issues in the relationship that have concerned me at times, and I've come to the conclusion that I can't see a future in this relationship, insistent though she is that I'm the one she's 'meant' to be with.

Problem: Currently, girlfriend is in the middle of a manic or hypomanic episode (she checked herself out of the hospital for the second time this go around, contrary to medical advice). Every time we talk, she attempts to press me with questions about whether I want to be with her.

On the one hand, the honest answer is no. She's got her share of good qualities and I have no desire to disparage her, but I don't think she and I are compatible, and as much as I hate to say it, the experiences of the last month have effectively eroded what feelings I still had for her.

On the other hand, giving her an honest answer at this point and thus breaking up with her is something that I (and my friends, and her parents) are worried that she couldn't handle at present, due to her current psychological state. (Especially since the beginning of this manic episode, she's been proclaiming her love for me very persistently; she even tried to force me to propose to her last time I saw her during spring break, and she insists that she's been receiving divine revelations to that effect. It's difficult for me to judge to what extent her feelings - as distinct from the actions expressing them - are simply a product of the mania.)

I haven't been replying to most of her messages lately (numerous phone calls, Facebook messages, Skype messages, etc., every day), since I've been unable to find a suitable way to deal with her inevitable questions. (Unfortunately, this means that she's been frantically trying to reach out also to my roommate and to my last ex-girlfriend with whom I retain a solid friendship.) Ideally, I'd try to wait out the episode and deal with this when she stabilizes; on the other hand, that could very well be weeks yet, even with her medication.

(TL;DR version: need to break up with woman who's currently in manic episode; want to find the 'how' and 'when' of doing it that both keeps me sane and also avoids being a jerk and/or unnecessarily harming her during her time of psychological vulnerability.)

In the current situation, I'm somewhat at a loss. Any suggestions, reactions, or similar stories?