Charlene grooms Wylla daily. It's a sweet bonding exercise for the pair, and the giver and receiver both seem to enjoy it.
Charlene has never had a problem with hairballs, so I don't worry much about any extra floof she may consume while grooming Wylla. Bean gets "Furminated" regularly, and her body seems to process any hair she does take in just fine. She'll cough up a hairball maybe once or twice a year.
I think it may be beneficial to Wylla - her digestive system is delicate, it's probably better if there's not a lot of floof passing through it.