Braces off and G5 trombone exam in less than month

[FiveHoursSleep]

DD2 has just had her braces off after 2 1/2 years and has been very happy with the results, but has discovered that she can no longer hit the difficult notes on the trombone. She has ASD and it's causing her a lot of frustration.
Has anyone had any experience of this and have an idea of how long it might take to get those notes back with some practice?

It took me a while to re-learn - longer than a month. Is there any chance of moving the exam out?

I would say it's possible.
I assume she has a good base level?
concentrate on warm ups and strength exercises - long and loud notes
and lip flexibility exercises in the lower notes.

better do 3 short bursts than one long one.

three short bursts a day I wanted to say.
good luck! trombone is such a beautiful and versatile instrument!