First up, wow! It really does seem as though there are a lot of complicated threads to tease through for you greenlotus. I do feel for you.
I thought of a number of questions as I read through your post. The big one was wondering whether any alternatives were discussed at the meeting if acceleration didn't proceed? We're there any other options raised at all given the complications with acceleration in your current setting, such as having an older sibling etc? If the girls do fight a lot, having them at separate schools could end up being a good thing but waiting until next year for a decent school doesn't sound reasonable.
It seems as though you have a major problem with your daughter's current teacher regardless. Is there any option there for change, such as another class? Can you discuss the teacher's less than supportive attitude privately with the Principal to seek a solution?
I find it disconcerting that your daughter has to be two grades ahead to get a one year skip! If she is two grades ahead she would need a two year skip.
How do you think she would cope at middle school? Can you scaffold any executive functioning problems that might arise? The physical differences look dramatic at this age but they even out. Our DD was tiny compared to her peers after grade skip and now she is taller than all her friends as she prepares for a second skip. It's not insurmountable as long as your DD doesn't have to play sports with the older kids. Even then there are yr 8s at our DDs school in the seniors team for some sports!
The fear over the testing prep is not unexpected. It is a big ask to take a test two grades up without a great deal of preparation so I am sure it looks daunting. Can you concentrate on three sections she is best at and leave the rest or do they need to see a certain level on all tests in addition to 75% on 3 of the 5?
I don't know why it is so hard. Doesn't it make your head hurt!
