Maestro

Hey guys,
I was just wondering, since a lot of you seem to know a lot about this insurance stuff, If my girlfriend drives my car ocassionally, (she doesn't live with me, has no car, no policy of her own) . Do I have to mention her to my ins. co? Is my ins. gonna pay if she has accident if I don't tell them about her? I have my own policy for my own car.
Any advice would be greatly appreciated