If a sitter decides she/he feels confident enough to handle your dog and gets bitten, then the sitter won't be covered by the Rover Guarantee. You should definitely have a numerous meet and greet and since you want the sitter to stay at in your home, you should do a trial too to see how your dog reacts to the person. Make sure your dog and the sitter are "friends" before you leave them home alone. Good luck :)
What's covered?
Vet care for injuries to a “Rover Dog”—i.e., a pet owner's pet(s) in a sitter’s or dog walker's care, custody, and control
Vet care for injuries to the sitter’s or walker’s resident pet(s) caused by a Rover Dog (in cases where the pet owner may be otherwise liable)
Physical damage to a pet owner’s personal property caused by the sitter or walker, or the sitter’s or walker’s resident pet(s)
Liability for injury to certain third parties caused by a Rover Dog
What's not covered?
Injury or damage that arises during a Meet & Greet or otherwise outside of the service dates of a confirmed Rover booking
Long-term vet care—i.e., care that extends more than 30 days past injury
Treatment costs for preventive care, or medical or veterinary bills resulting from an illness or a chronic or pre-existing condition
Preventable conditions such as fleas, ticks, or parasites
Damage to a pet owner’s property caused by his or her own pets, or damage to the property of a pet care provider or someone related to or residing with the pet care provider
Injury to the pet care provider or pet owner, or someone related to or residing with the pet care provider or pet owner
Some stranger in her home could be a problem even after meeting. Do a few meet and greets and test dog with another meeting while your out of site ONLY if m&g goes smooth. Home boarding at sitters house might be a better option depending on why the dog might bite. Fear, Territory, Aggressive?