Have you had a chance to communicate any further with the teacher than email and being pulled aside briefly? I'd ask for an actual conference before I'd agree to pulling her back in math - I think it's really important to have both your dd's and her teachers input on what they each think is happening. It could be any of 1000+ different reasons and it's (imo) more important to try to understand what's up before making a change. Hiring a tutor who can work closely with your dd will help you understand what's going on too, because you'll be able to get direct feedback.
FWIW, one of my dd's is a really creative loves-writing-etc type of personality, and she's gone through huge cycles of being great at math vs completely not understanding what was going on back to being bored because it's too easy - all over the map. Part of what looks like total randomness in where she falls in math really isn't as random as it looks - different types of elementary-level math skills require different types of reasoning, and what the dips and swings for our dd are about is really an unevenness in those abilities - and it took awhile to realize that because of the nature of spiraling math programs like EM. She'd be struggling for awhile, and by the time we'd find out about it and were trying to figure out what was up the class would have moved on to something else then she'd be back on top of things and doing well.
Another thought for you, just something to keep in the back of your head - 2nd/3rd grade is the time at which a lot of us 2e parents saw our kids actually struggle for the first time. This is not the same thing as saying "all kids even out in 3rd grade" - instead what happens with a lot of our kids who have challenges is they can get by in early elementary with compensating, but the change in expectations, type of work, and workload around 3rd grade often tips the coping bucket over just enough that it starts becoming obvious there is a challenge. Please know I'm not saying your dd has a challenge!
Best wishes,
polarbear
