First, having worked with little ones for 20 years plus, I am going to have to disagree with one of the previous posts which stated this should be concerning to you. Please, know that there are lots of very bonded, highly attached children who show a natural curiosity and inclination toward other adults and kids, even to the point of ignoring their parents. This is not abnormal, instead this suggests that your daughter is so reassured of her bond with you that she feels safe to explore her extended family and relatives.
What a lovely treat for her, for them, and for you. I'm sorry you misinterpreted this as something it isn't. As AJC listed, *those* are the hallmarks of attachment disorder. I've worked with a few kids who have had these symptoms and they were extremely difficult for anyone--their parents, teachers, peers-- to connect with. Watching a young child flit from adult to adult would suggest to me that she feels safe, loved and a true sense of belonging with her family; that in fact, she's very secure in her relationship with you.
This is completely different from kids who tug and tug on mom's elbow or pant leg, only to be ignored, who sadly go off to find another adult to meet their needs. It doesn't sound like the case from what you describe.
My son is categorically very much like your daughter. He has done this since he was about 3.5-- he wants to tell everyone every.single.thing he is interested about. He would make up huge fantasy stories to share with the parents of other kids at preschool. He's very loving, affectionate and bonded with us, and I believe his desire to be outgoing really has a lot to do with being ready to explore more of his world.
I also agree with everything Laurie A. wrote. She regularly gives great advice and her post is spot-on. I hope you find a way to enjoy your daughter's excitement toward learning more about her relatives and how she fits into her family. Hugs-- it can really surprise us when our kids begin to ignore us at first, huh?! I've had those same pangs too.:)