she will be fine

OHSS is not that uncommon in young donors. My SIL had it happen to her and she was 40...your donor will be absolutely fine in a few days time.
You need to focus on your transfer and your embryos. The last thing your donor would want is for you to stress yourself out and the cycle not work (not that stress is definitely related to success or not..no one really knows) after she put in the time and energy to get you those eggs.