Why is my teen(15) daughter mean to me around this boy?

I am assuming you are the mother.

15 year old girls can get jealous of their mothers. Be sure you honor that he is HER guest. Be an observor at an event such as a dinner. She may get threatened that you are getting too familiar with him.

I had a three year old come up to me and hit me because I was talking/laughing with her grandmother. She didnt like it that grandma and I were talking and grandma's attention was diverted to me.

That said, HOW she reacted to you is something to talk to her about. Does she act like that when she doesn't get her way? Does she swear at you often?

My 14 year old does this same thing - but with toward her older sister.

My take is she is trying to be cool - some how by being mean it is showing she has a "coolness" to her. It is more showing off to the boy than anything. Basically she may be a bit insecure and doesn't know how exactly to behave in order for the boy to like her.

It's a strange behavior but what isn't with a young teen girl?