Why doesn't she wanna open up to me?

Anonymous
So I was at a party about a month ago and I met this girl. When I met her she didn't conversate with any of us just the people she knew. She seems very intelligent and she has high morals. We became semi-friends and I asked her on a date. She accepted it surprisingly, and it was great! She seems cool despite her rigid-tough, aggressive exterior. We have been going on dates ever since and I'm asking her to be my girlfriend on Saturday on our third date. The problem is, she isn't opening up to me. Yes, I already know like her favorite color simply things like that but I'm afraid that I don't have enough information about her to potentially be her boyfriend. She doesn't tell me about things that happened in her past etc, seems like she is reserved. I really like, what should I do, why is she like this?
Why doesn't she wanna open up to me?
2 Opinion