Will a shy girl call me ?

There is a girl in college that I have for my English class and she is a very shy girl. We have been talking for about a month I found out that she likes me and I like her to. Every time before class she tells me hi sometimes with a smile and there's times when she starts the conversation with me or ask me questions about school work. About 2 days ago I gave her my number, I just told her hey if you need anything call me or if you wanna talk give me a call she just said ok and she said yes with her and said thank you. When I gave her my number I wrote it down on a sticky note but I had the number ready I hand it to her she got it and looked at it for a little bit and she took the top sticky note from the top or the stack that had my number and gave me the sticky note stack back to me. And she put my number in her bag right away is that a good sign ? I been wondering why she has not call me, Is she to shy to call me ? or did I scared her cause I gave her my number ? what should I do ? remember what I said she's a very shy girl. When should I ask her out ? please help!