My 14 year old daughter likes her 23 yr old brother best....?

She mostly only talks to him and follows him around.She has always done this and favored him more than anyone..more than her older sisters and when I had her baby brother,she didn't even care about that.She has always been uncomfortable around my husband and in a way avoided him.She never really talks to me just to talk..she only talks when I ask a question.She talks to my son all the time.He's a dropout and still lives with us.She follows him everywhere,when she's not doing that,she's alone.I ask her if she ever wants any of her friends to come over she says "No" and that she hates them.She says she hates everyone but her brother.She only hugs him goodnight and only tells him she loves him.One of my friends says it's incest (I don't think it is.).I asked my nieces to talk to her,but they tried to make her hate him and said alot of things they shouldn't have.What to do?