...and the other kid is eleven (And a boy? Does that matter? I can't tell. For SmallBeaver it wouldn't - but the boy? I don't know anything about nice 11 y/o boys...)
What do I tell her? There is no way his parents will understand him having a 6 y/o friend. But on the other hand, she's massively socially successful - but doesn't truly connect with kids very often and it seems a shame to just let it go.
ETA - they met at dance camp and hung out quite a bit - he grilled her extensively about her grade level (probably because of vocab) and apparently got the real answer, rather than her usual response for people in general which is, "oh it's homeschool, so we skip around."