Sounds like a lot of good things happened. Love the quote from the principal, "Why are there so few services at the gifted end of spectrum?" ...As many of us have been wondering for decades!
From a distance, the comments as to "what if she learns 4th grade math before she leaves the school," are kind of humorous. Perhaps better to wonder, "What if she finishes 4th grade math before she leaves kindergarten?"
I think the two of you must have done a wonderful job to have this go so well.
A couple phrases that might be useful, which I didn't see suggested. "I/we really need your help." "We're all in this together." "We're trying our best to research and understand what might be best for her, and really appreciate your help." "We're as amazed as you might be by this, and are really being put through our paces to try to keep up!"
All geared to creating language around the concept "We're all a team trying to do our best for her." Metaphorically, drawing you all onto the same side of the table, vs opposite sides, in creating a program for her.