Threesome?

So me and the hubby have been wanting to do a threesome with another chick for a while. We are on vacation at his sisters house and he told her and she invited one of her friends over. We went out to the club and then back to the house and got I the hot tub. Hubby was rubbing both of our backs in the hot tub and even told her that she could join us in our bedroom instead of sleeping on the couch. She said no that she just wanted to sleep. She had to get up early for work. And honestly we all stop much to drink and we're feeling not so hot. Anyways I need advise. She is going to come over again tomorrow. What do u do? I am new at this and have no idea what to do or say. I'm pretty sure she is into U.S. Though.