My significant other and I both have our names on the lease for our shared apartment. We are not married. She has a renter's insurance policy that she claims is enough to cover both her belongings and mine (I'm not 100% sure on this, I would have to thoroughly evaluate everything we own and verify that her policy covers all of it). Our apartment requires renter's insurance but they seemed satisfied that only one of us had a policy. Should I get my own renter's insurance policy anyway to protect myself or is this a waste of money?
The apartment complex is satisfied because they have a clear company to go to in case of a problem. However, this has nothing at all to do with your belongings.
Renters insurance will cover the people listed on the policy. If you aren't listed, then you and your stuff isn't covered.
It's better for you to acquire your own policy. As she has her own, you wouldn't need to include her. Once nuptials are tied (if ever) then consolidate. However, you two break it off then, well, this is one less thing to worry about.