When you say "next year", when does that mean? January? And when do you think is the very last minute when you could make the decision? Writing could come together very quickly, like days, if our experience is anything to go by.
And what limits her writing at the moment, would you guess? Fine motor skills, or examples, or interest, or what? Does she do detailed drawings, neat colouring, etc?
And how closely did the school consider the grade-skip: can you take from their willingness that they think her writing will be good enough for the year 1/2 class, or do you think noone's really thought about it properly?
Good luck. (We have similar issues: DS5 is not accelerated, but had it not been for his writing we might have considered it.)
