I'm really surprised the teacher is letting other kids pick her up, too. Particularly when she objects, but there's a big safety issue there. (My DD7s best friend is a towering 9yo a good 6" taller than DD. BF picks up DD when they're playing together, because they both think it's fun. About 10% of the time, both kids end up toppling over.)
Assuming your district doesn't require mid-year skips, and assuming that your DD is not complaining, my vote would be "wait and see," particularly because your DD is doing fine socially. I know mine had a huge jump in maturity level at about 6.5, and yours may, too.
As far as maturity level goes, though, I will say that my DD is perceived by adults (including experienced teachers) as being mature. But what they mean is the "can handle older-kid classroom expectations" type of maturity. Older-kid little-girl drama has been a big issue for us, because she is not particularly mature in that respect. I'd anticipate that would be an issue for a kid who's being physically handled against her will, too. Not that older kids would pick her up (I agree that they'd be more likely to control themselves), but that they'd do different things that she wouldn't like.
