One Mother of a problem

Well, long story short I really like this new girl (I'll call her Ren) at work. I told Ren I like her and asked her to the county fair and carnival. She said yes but told me her mom wouldn't let her go. My manager gave me 2 free tickets to the movies for coming in an extra hour early and I am really wanting to take Ren but most likely I am going to have to go through her mother, how would be the best way to do so and gain her mother's trust?
From what I have gathered, her mom is a smoker and not very pleasant to be around. Any advice on how I can get her mom to let her go to the movies with me will be more than welcome!!!! :love: