Thanks so much for all your responses. I met dd's Spanish teacher for the first time last night, and she went out of her way to tell me that dd "picks up Spanish incredibly quickly." I think I will see if I can find someone to do an assessment of her, just so I know exactly where we are--whether we have a moderately gifted hard-working kid or someone with exceptional gifts who needs more individualized treatment.
I haven't mentioned before that the school she has been in until now was a Montessori school, so that she wasn't quite as stuck sitting still in a classroom being bored. When the work seemed boring to her she may have had more freedom to find something else to do, even though she would complain about the fact that "we're spending a whole week learning integers." She's very rule-conscious and a bit perfectionistic. I'm a little nervous about what will happen in her new school when she really has to sit and listen, if the material is too easy for her.