if I understand your question correctly, it sounds like you're concerned about a boy who is too attached to your daughter. You don't say how old the kids are and that makes a difference. If, for example, we're talking about pre-schoolers, then it would be appropriate for you to talk with the teacher about your concerns and let him/her deal with it. On the other hand, if your daughter is old enough to speak up for herself (and she is as bothered by the boy's attention as you seem to be) then she should be the one to talk to the boy. It's important that we teach our children (girls as well as boys) to speak up for themselves when they feel encroached on by others. Helping your daughter set healthy boundaries is a life-skill that's never too early to learn and practice. if you daughter has directly and respectfully told the boy to "back off" and he's still in her space, then I would get the teacher involved. If that doesn't change the behavior, then I'd suggest you talk with the school administration and set up a meeting with you and the boy's parents.
I hope this helps.