Please help I'm in a sticky situation!?

Ok, so my mom and dad are going out of town on Saturday night, and so I invited one of my friends,lets call her Tina, and she said she couldn't come, so I called another friend, lets call her Cindy, and she said she could come. Tina and Cindy are enemies. So Cindy is coming over to my house and last night Tina texted me and is like "my mom said i could go!!" and i said "sorry, I already made plans!" and then she said well my mom already hired a babysitter, and took work off so I could get to your house, and so I was like well you said you couldn't come so I made plans!! SORRY! and she goes you don't get it, your being rude, you invited me FIRST! And so I said well you said you couldn't come so I made new plans, and so she is waiting for an answer, what should I do?!?! If Tina comes over Cindy would hate me, and if Tina doesnt come over she'll hate me!! PLEASE HELP!!!!!