Why would a girl go to places I suggested we go too with another guy?

So I have been friends with this girl for a while. We were planning to go to the cinema to see a film she wanted to see. However, I saw a snap from her seeing the film with another guy on the day we were going too. Is she annoyed at me or is she trying to make jealous?

Why would a girl go to places I suggested we go too with another guy?
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