if you perform "bareback" you are taking the risk of contracting HIV regardless of if the other took a test or not? , tests are not 100% , condoms can break! , it's a bit late for the model and maybe if they had used a condom there might have been a case here.
i'm sorry i can't be more sympathetic , if maybe the film produced had used condoms and it broke in the performer i might be more understanding. ( interpreted: ..."if you play prepare to pay!"... )

jim