I developed Bell's palsy during the first lockdown - my GP was very annoyed that I hadn't called immediately as treatment for stroke works better if started straight away. He did several tests to make sure it was not a stroke.
Luckily mine was BP not a stroke so no treatment just time. Some sites recommend exercise but it may be that done too soon it can make it worse. If she does want to exercise make sure you are using a good physio site (ie someone with real qualifications for treating BP)
Evidence that exercises help at all is very limited:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136559/
I only had a mild attack, and it has mostly resolved now, just a bit of drooping when I'm tired.