Tell her to never ride in public transportation, get on an airplane, sit in a conference room then.
Because it's almost a certainty that at least one person will be sick in those scenarios, not to mention in a closed room.
Also, tell her to stop touching fruits too, there is an insane amount of germs on the skins/shells of fruits.
Then, tell her to use a brand new grip after each hitting session.
Lastly, tell her to stop breathing, because it's with certainty that there are viral particles in the air she's breathing. Whether or not she's immune to a particular flu strain is a different story, but she's literally inhaling these "germs" with each breath she takes.