Girls, why would you start acting distant with the guy you are seeing?

Anonymous
I've been seeing this girl for abut 2 months now, I recently told her a few days ago over text that I wanted to talk to her about becoming official boyfriend and girlfriend. Since then I have seen her once and we couldn't really talk about it because her friends were around. I invited her out to lunch and she said she was tired and said I could go to her room if I wanted, so I did and her roommate was there so it didn't happen. It's been 3 days and it seems like she is avoiding me and not even texting me anymore. I saw her at my fraternity house last night after not texting or talking at all that day and she just acted like it was nothing. I said hi to her and she just gave me a quick hi and left. Then I texted her later and she didn't seem interested in talking to me. I texted her goodnight later and she didn't respond to that. I don't know what to do...
Updates
+1 y
I asked her out to the movies before she started ignoring me and when we talked last night she said she still wanted to go...
Girls, why would you start acting distant with the guy you are seeing?
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