No, condoms do not cut the risk of performers getting HIV, not significantly.
Condoms reduce the risk of getting infected from _any one performance_. If a girl does, for example, a dozen scenes (I'm not sure of the number as I haven't calculated it) then the odds of infection are about the same with or without a condom (when the partner is HIV+; if the partner is HIV- then the odds are exactly zero with or without a condom).
So yes, a one hit wonder will increase her odds with a condom but most girls will not.