I would suggest that subject acceleration by 2 grades or more puts you in a difficult situation in 4th and 5th grades. The 5th grade teacher will usually have resources to differentiate to 6th grade, but not further.
A aubject acceleration could be considered as a step in phased grade skip acceleration.
I am super not impressed with all arguments about "holes" in grade skipping.
In math, my son skipped from 1st to mid-4th grade, did 5th grade in 2 months, only did part of 6th grade before skipping to 9th (in 4th grade). This was through the local district's virtual charter school.
I put him into public (5th grade), where he was grade skipped mid year to 6th, and subject accelerated into 8th grade math. The only holes are differences in curriculum, and they're seriously no biggie. He could have them covered in a week or two of self-study.
One would expect my son would have tons of holes. Not really. If the virtual charter school and the bricks and mortar school used the same curriculum, he would be fine.
I think we underestimate our children's capacities. I think we often underestimate their social skills too. My son was a loner, social reject in elementary school until 5th grade he found a friend in his classroom who was grade skipped 2 grades. Now that he is grade stepped he has a lot of friends. I can't even keep track of them all.
I did not expect it!
The only way to know is to try! Don't tolerate them basing decisions off of fear and assumption. Ask them to try. If it doesn't go well, move her again. Acceleration is a bit of guess and check sometimes!
