Nuh uh, I refuse to believe it. She made plans when he had already asked her out the day prior???
It has to be the case where she's actually lying about going to see the play, so she can throw a surprise party for mc... Because if someone were able to go back on a promise, on a whim is pretty awful. Still though, if that were the case, it likely means she hasn't developed feelings for him yet. Shes aware of him, but thats not enough to put him before her wants.