I've read some of these responses and just want to add a little "social-worker-ism" to the subject of tattling. It is always a slippery slope to ask children to stop "tattling". There are so many things that can happend to children that they need to share with mommy and daddy. At such a young age, how is she supposed to decided which are the really important things and which are things that annoy you. I always encourage my children to tell me anything they like. Whether it is petty or not. You can actually use those petty things, like playing well with others, as an opportunity to teach socialization.
I have taken my children over to my girlfriends houses, and there are always age differences, gender differences etc. If you want to continue to be a part of this group, may I suggest that you provide your daughter with something special to do while she is there. Crafts that she can do by herself, interactive DVDs with singing and dancing. Some small portable DVD players can be reasonable. You might even check at a pawn shop or on-line for a refurb one if the retail price is too much. I have even purchased short "books on tape" with a headset and kid friendly cd player. Even if the other children do not join in, she may see the visits are special because she will have special activities reserved for that play-date!