parker

Because look at the way Lydia behaves around boys. 

When she’s around Stiles she’s a hybrid of who she is with Allison and who she is with Aiden. Which I think is a really good thing. Lydia and Allison, in s3, had a really pure friendship in which Lydia actually behaved like the person she is instead of who she was always pretending to be. Which was a hugely significant development for her character. Allison is probably the character on the show, aside from Stiles, who understands Lydia the best. 

With Aiden, it was all about sex. Both of them knew that Lydia was 100% in control of it. She was the one who incited, she was the one who decided what they did and when they did it, she was the one who kept Aiden at bay. There was this flirty confidence to Lydia with Aiden that you can see when she’s around Stiles, especially in 3b. But it’s the flirty nature mixed with the friendship that she has with Allison. So he’s her close friend (best friend, at this point, even though he doesn’t realize it and doesn’t act like it) who she can be herself around, but she also plays with him the way she plays with Aiden.