Hi-
I have a fourth grader also... She is HG, and was tested when she was a second grader. She is accelerated 1 year for math, and receives gifted programming for everything else. Even among other gifted students, she seems to stick out socially and she feels different, even though she does have friends... I think once you get into the upper ranges of gifted, it gets even harder to find peers who care about the same things you do. She also is a big thinker, and feels like she always needs to be doing something. It seems like she always is looking for a cause.
She liked the book "The Gifted Kid's Survival Guide." Galbraith is the author. She also joined a Mensa children's group, which has given her access to a group of intellectual peers. You might look into similar programs in your area. Mensa varies from state to state, but they might have a children's group or family group.
