If she lives with you-roommate.
If she doesn't live with you-friend.
The insurance company doesn't REALLY care.
It would be more important to establish the depth of relationship if it were medical paperwork.
With car insurance, that doesn't effect how much they are covered, it only establishes for the company (in their mind) how frequently they may have access to the car. A roommate is considered all of the time access, whereas a friend, not so much.
(dealt with this ourselves and asked a friend who works in car insurance)
"Love As Thou Wilt"