Margot expected to have a lot of fun on her vacations, meet new and interesting people, and hopefully have sex with them. She hadn't been ready for the Mitchel's.
Both Andrea and Layla were gorgeous, and they flirted with her quite heavily, but they did so independently of one another, and Margot wasn't sure she wanted to get in that kind of mess. She wanted to have fun, yes, but she didn't want to ruin a marriage at the same time, that was not the kind of girl she was.
They were making it difficult for her though. Margot was soon driven to her limit, did something she shouldn't, and then had to face the punishment for it.