So I've been hanging out with this girl and we have a history together. Lately she's been acting flirty and throughout the day I've caught her starting at me and stuff. At night, we will sit next to each other on the couch and we will slowly get closer and closer. Then eventually we will be right up against each other and she'll typically put her legs over me or something. Then after about 5 minutes she'll get up quickly and say like "I have to sit somewhere else" in a rushed tone. How can I make her not leave and stay instead?