I agree with others that you might want to look at whether she's being distracted by the new setting (K is a big change). Or she might be worrying that if she does all these things that she can do so well, she'll stand out and be different from the other kids. Not all the other kids are doing all these tasks perfectly, even though the teacher says they completed the tasks.
She also may have the "I do not perform on command" thing that many younger kids get for a period in their lives. A lot of toddlers are this way -- "Please sing that little song for Grandma! The one you sing so well!" "No!" -- but it can affect kids your daughter's age too. You want me to do this? Really? Sure, but only as much as I want to do. You want me to finish it? I don't think so.
It's about control. "Teacher can't MAKE me do it." This isn't because a child's wicked bad! It's because a child is, well, a child, and feels she has little control over any part of her life, and THIS is one thing she can indeed control. No one is going to make her pick up that pencil again and draw even one more circle, no sir! She is in control. She has zero realization that to adults, her actions are interpreted as her being "in the slower group," as you put it.
This is truly where -- as others rightly note -- the teacher needs to step up. Have you been in and talked with the teacher, at length and in person, and without your daughter there? And with the school counselor also present? I would do that, pronto. You say the teacher's amazing and that may be true, but the teacher now needs to work with you and the counselor to find what will motivate your girl. The counselor can help you both figure out what might motivate your child, and the counselor also can give you some ideas on what to say to her to help her understand why she needs to finish work.
It sounds like your daughter is not a kid who is interested in pleasing adults. That's not a character flaw, just a fact-- some kids are motivated by wanting to make the teacher happy but others feel no motivation at all to please the teacher. So the teacher and you need to figure out her motivation, and come up with some system that works both at school and at home. It might involve making your daughter VERY aware that you will know every day just what she is doing in school, and what she does in school will affect what happens at home. If she wants control, she might actually respond well to being given extra responsibilities in the classroom and "chores" at school that are hers alone. These would be rewards -- not punishments! - for having a good, cooperative day.
I agree with Gamma G that your daughter might not be seeing the teacher as the authority figure here. Did your girl do preschool? That helps kids learn to follow directions from adults who are not their parents etc. If she did -- was she like this there? If not -- she may just be catching up to the idea that an adult who is not you is indeed allowed to tell her what to do and to push her to complete her work.
First thing would be to meet with the teacher and the counselor and not in a rushed way or when you have to get somewhere else soon.