If she is happy and doing well then I guess things are going okay. She doesn't have many friends to pick from and it takes time to make friends. I can understand her being reluctant to stick her neck out relatively early on.

Can you talk to her teacher to get a better sense of things / hopefully put your mind at ease? See if the teacher knows she's smart... Whether she is encouraging / accepting of that or whether there might be something a bit more sinister / toxic going on with promoting the average or trying to protect the ego of some other teachers kid or something like that...