JMO, but it signals a potential "big" problem to me too. FWIW, we've had very similar concerns with our dd7 who is in second grade - your description of your dd matches our dd in almost every way. We had our dd go through an educational assessment and dyslexia screening this winter, and what we found was very different than what we'd anticipated finding. We *thought* she might be dyslexic, but instead found out that she has a definite challenge with associative memory and possibly a visual processing challenge.
My suggestion is to seek out an eval now - either through the school or a private eval, but definitely don't wait. If you look around in class at the writing other kids are doing, I'm guessing most of the other third graders aren't spelling like your dd is spelling.
Best wishes,
polarbear
ps - re the teacher saying your dd is working too fast/not trying - I have two 2e kiddos, and both have had teachers say that. That can be SO damaging to a kids' self-esteem when they really really are trying, and it's so important that if there *is* a challenge for your dd you find out now and put a name to it so your dd doesn't have to be caught in a situation where she is trying and the adults around her at school don't believe she's trying. I found that for my ds in particular, having teachers not believe he was trying not only hurt his self-esteem and led to a ton of frustration, it also really damaged his view of school and it took a lot of getting him into a better situation before he had any trust in his teachers.
Last note - it's possible it's nothing, just as the teachers think. If you go through an eval and find out it's nothing, you've lost nothing. OTOH, if you don't look into what's up and there really is a challenge, school is just going to get harder and harder as the years go by.
