Why is she acting like this?

So this girl and I met a few weeks ago at work and we got on great had a lot chemistry, she laughs at most of the stuff I say, she plays with her hair etc and shows other signs of interest. She mentioned at lunch when we were sitting together we should do something together one weekend but suddenly after a few days she’s acting distant, I’ve asked her if everything is ok and she says yes but seems like she’s only acting like this around me. It’s like she’s showing me mixed signals being hot and cold. Sometimes I catch her glancing at me and then she looks away. She’ll linger around where I am then other times it’ll seem like she’ll run away. I feel like I might have done something wrong I don’t understand what changed. I thought it would be best if I gave her space and now she looks mad frowning and rolling her eyes at me.
Why is she acting like this?
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