This is really a. Good question. Be kind, but firm. Suggest She seems to be so busy that it seems she doesn't have the time your property requires.
If you want to, just write her a kind email saying the same things and tell her you would simply like to find an agent who has more time for this project,.
Thank her for what she has done and give her your best wishes for the future!
A little kindness goes a long way. We never. Know the difficulties in another persons life.