Not really a relationship, but still. I'm feeling pretty down lately. For the past two months I've been working on a university project with a girl. Even though we've been passing by each other for 3 years in lectures and such, I never gave her much notice, she was just another pretty face in the crowd. As we worked together, we started slowly getting to know each other and like each other. It was really gradual, we started spending more time together even when not working. A week ago, out of the blue, she went on to tell me some very personal stuff about herself, that she claims only 3 other people (her close friends whom she's known for 10+ years) know. I didn't really know how to react to that at the moment so we parted ways that evening in an awkward atmosphere. The moment I came home and signed into msn, she messaged me with "hey, I'm sorry if I overwhelmed you with what I said" - indicating that she was worried she might've scared me off. I said that I find it flattering when people open up to me, because it means they find me trustworthy. Then we talked some more where she revealed more, and when she said "I don't know what's going on with me tonight, it must be sleep deprivation from studying", I responded with "yeah, well that sure is a convenient excuse :P". She said "well ok, that's not really true, I become more talkative when I get to know someone better and like them".
The next few days we talked and talked, it was really idyllic. We throw around sexual inuendo like it's nothing, make each other laugh all the time. We're both single, but that's more of a consequence of REALLY tough work we have to do school wise, we literally spend 10 hours a day, 7 days a week either studying or working on projects.
This week, on the other hand, was a total blackout. It's like something changed drastically, her disposition towards me has gone from what I described above to just "polite" and kind of cold, talk has been reduced to just work and I feel like there's a great big wall there that I just can't get past and don't understand why it's there in the first place. It's really frustrating and it's on my mind constantly. I don't want to nag about it, because that will only come across as needy and insecure.
Though writing about all this in a thread on a superhero forum probably isn't much better in that regard haha.
NOTE: There is one case known to me, when she was leading a guy on, only to tell him that she was just having fun when he confronted her, it got to him, his grades dropped, he dropped out of uni.
TL;DR
Guy meets girl. They get to know and like each other quickly, she opens up to him, shows interest and insecurity, he encourages her. Girl starts suddenly acting cold and distanced. Guy gets frustrated and can't stop thinking about it. Girl has a history of leading people on.