I think she just likes the attention and figured out one way to get it from other people, including boys. Show/tell her about other ways people get noticed, tell her about inner beauty, deeds, character, brains, etc. I think she is experimenting at this point. Just have these conversations often and not when she has the behavior.
Another thing, as I remember myself this age, to get attention from boys is much easier than from girls, and it is sort of a quick fix to feel good about yourself :) Have a talk with her and explain that her behavior (she probably thinks is very innocent, I sertainly did) may be interpreted differently by boys/young men and that a girl needs to be careful to avoid putting herself into awkward situation or starting rumors. She may understand that reasoning.
Another idea, I teach that to my son, just a lot of exersises in self-control, good for boys and girls. As their hormones fluctuate kids get excited for no reason and sometimes in a very unusual situations, it is good to teach the kid to apply internal brakes when they are crossing the line (sometimes my son knows where that line is and sometimes I have to point it out, we have a special sighn for that).
I think it is great that her dad is involved as well.