Here is a good article on sharing renters insurance with a roommate
. In my personal opinion, sharing a policy with any person who isn't a spouse is not a good idea. The amount of coverage on the policy is split in half and any claim made by the other party will also be attached to your insurance record. There is also the issue of separating the policy if you two happen to part ways. Renters insurance is generally inexpensive so you wouldn't be saving a lot of money by combining your policy, and the potential headaches that could arise should anything happen between your and your girlfriend are reason enough to keep it separate.