Possibly 2e first grader quietly refusing to participate in school

Can a kid be "gifted" and not interested in learning at school? OR maybe just not interested in learning first grade level stuff (she has not mastered it, so it's not that)? Or maybe the entire approach to learning at her school is just such a turnoff to her that she's in full on Bartleby the Scrivener mode ("I prefer not to").

Our 6 year old daughter has been getting reports of being disengaged, like not answering the teacher, not working on what is in front of her, sometimes getting up and wandering around, and declining invites from other students to join in a group activity.

We got her a (somewhat abbreviated) neuropsych eval to check for ADHD since she had some hyperactive and inattentive flags, but she didn't qualify for a diagnosis. She did however get identified as gifted with 99th percentile in verbal, 98th in visual-spatial, and 70-something in processing and working memory.

However, she says she is a slow worker. The teacher says she isn't finishing often because she is talking to others. Though the latest report makes it sounds like she's not forming good relationships with other kids this year (not a problem last year) :(

Though she tested as gifted, she isn't blowing anyone away with academics. The usual explanation for gifted kids not performing in school is "they're bored because it's not challenging enough." It's hard to see that's the case, because the work is not easy for her either. She does well on standardized tests but not day to day work.

BUT, maybe it's hard because it's boring ass worksheets instead of a science or art project or something cool. But then she declines to participate in what is considered (by her school anyway) to be more fun learning activities in the class (but maybe those are not that great either). Maybe this is rebellion because she feels bad or anxious about the whole thing?

Or... perfectionism leading to paralysis?

Her twin (call her Girl B) is probably gifted too from appearances, but she just blazes through the worksheets, impresses her teachers, and then gets more fun things to do. She's in a different classroom. Girl A gets stuck, doesn't finish anything, doesn't get the fun, and then feels bad when the teacher isn't giving her good feedback. Maybe Girl B has an innate desire to crush challenges and win at everything, and Girl A just wants to do her thing for enjoyment (usually creative stuff of her own design).

The neuropsych when he did her eval said maybe Montessori or another hands on, more stimulating program would be better suited. As we look at schools it is hard to know what kind of approach would excite her out of her refusal to engage.