<human>: Condense the text into a few key points

So I met this girl about 3 months ago. We're introduced through my sister on Facebook and we chat for a good 10 hours the first time. We then chat on and off for a few weeks. She seems a little eccentric, but I put up with it for a while because she keeps baiting me with the promise of sex (I know this seems really shallow, but I'm not doing well in that department). So we finally plan to meet, I go to her house and we hang out for a while. It doesn't get to sex, but comes close. We do the chatting thing for a little while longer, until we plan to meet again. This time is much like before, except we end up having sex at her place. Shes not on any birth control, but I used a spermicidal condom (hopefully better than regular ones). We chat on and off but by this time I've taken keen notice of her eccentricities, and deemed that shes full on crazy. She keeps pushing a relationship and I really don't want this to go any further than it has. Every time she finds some way to manipulate the conversation into us agreeing that we are together. I can't bring myself to tell her that we aren't. This whole time my sister has been talking to her and has found out that shes cut herself in the past and has threatened to do it again. Her home life is really unstable and its clear she has some major emotional problems. In the past few days shes told me that she hasn't had her period since we've been together (almost a month ago). I'm telling myself its because of the stress in her life but I really don't know. I don't know if and when I do tell her we aren't together, she will hurt herself. This girl really is obsessed with me to the point where it makes me feel uneasy. I just don't know what to do.
<bot>: Girl has serious emotional problems. She has tried to, and threatened to kill herself. We had protected sex, now she is late. She thinks we are in a committed relationship, I want nothing further from it.