Why did she turn me down?

Ive started to hang out with a mutual friend more on our own terms recently. We have class together, we've gotten lunch a couple times, she's come over to watch a movie. yeah.

Shes a shy girl but when were together I get her to talk and laugh. After class today I asked her out for dinner. and she said "i can't go out for dinner with you" I half laughed and said whys that. and she said shed talk to me later.

I know she's single and we've been talking a lot lately. One of our friends also told me she liked me. We usually text each other throughout the day. so why this rejection?

All I can think of is she's trying to mess with my head or she sees me as a friend. but I've been really careful not to fall into that area.
Why did she turn me down?
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