This girl keeps spreading her legs and exposes her underwear when you are around She also ruffles your hair does she like you?

Two choices.

1. She likes you and the only way she knows how to show it is by acting like a complete slut.

2. She's a complete slut and it doesn't mean anything.

You know you. You probably know a little about her. If you're the type of guy she would go for, then maybe she's into you. If she's the type of girl who is into everyone, she's not into you and it may even be a cruel joke to her.