I want to have sex with a girl but her mom won't let her do anything?

I am going to have sex with this girl I like and she has said yes to it but her mom won't let her going anywhere so I was wondering should I say we are going cinema and I will meet her there and when her mom goes I will take back to mine and have it and then take her back to the cinema for her mom to pick her up and I was just wondering would it be a good idea and peps don't say no or anything stupid.