Birthday invitation opinions!

Ok so my daughter received a birthday invitation on Monday for a girl in her class. It's next Sunday and the little girls house. Rsvp to mom. Great! I marked it down to attend. Well on Tuesday she received another invitation for the same girl but from her step mom. It's going to be next Saturday (the day before moms) at a popular bounce house and arcade place. So now I'm torn. I've never had this happen before. Do we attend both? Do we pick one if so which one? I feel most kids are going to pick the bounce house place because it's more fun. But I feel bad for the mom because she's spent money for her daughter to have no one show up. What would you all do? It's a little girl from her class.