I understand your concern!!!
If your vet is concern about her size or weight, then you should wait.
My vet wanted to wait to see if Momiji will be at least 3lb.
Well she still isn't 3lb yet and she is almost 14 months old.
I went ahead did the spay at 10 months old when she was 2.3lb.
She did great.
She never came to heat so I was luck on that section.
Dakota is sooooo cute so I will pray for you if you decide to go forward with the spay.
But I'd say you don't have to hurry yet!!!!