Relationship Help?

I need some help! I've been going on dates with this girl and we've been talking for almost 7 months now. We go to the same college and went to the same high school and I've always considered her my friend. Everything has been going great! We talked everyday, been on numerous dates, and we hang out often, usually when she's at work I'll stop in for ice cream and we chat for a little. I really like her and she really likes me and we're seeing where things go. Not rushing it. But a week ago she told me she was going to take her friend out for lunch for his birthday, and that's good for her to do that stuff but since then, she's hardly talked to me, she won't even text me back. She told me she enjoys spending time with me and always tells me how sweet I am and now I'm lucky if I get a "hey" from her. I just feel hurt, we talked about a future and things were really looking up. I don't understand why she would be ignoring me, I know this friend she took for lunch and they were in a relationship through half of high school and I'm afraid she rather be with him. But she tells me she thinks he's a creep. I just can't understand how one week we are going on a date, talking to each other until late at night, and seeing each other. To not even being able to talk to her. I need help to get pasted all this or maybe someone can give me some understanding, or some advice on what to do. Thanks.