How do I go about taking someone off a lease? She has a restraining order to stay away from the house, so can't I just get the landlord to take her name off the house, or does she have to agree to it?

Your lease and that restraining order are not related. Unless all 3 of you agree the lease can't be changed. Leases are usually long term but retsraining orders are not. Landlords have no reason to agree to this and I'll bet she is not going to agree to anything at this juncture.