If she was taught to lunge properly then once you start lunging her it should kick in and she should remember "oh when she says woah, or when she turns her body, im supposed to turn IN to face her. Not give her my butt."
I would also work on her yielding her hindquarters while she's haltered. Make her realize that she never gets away with it. Whether she's loose in the field, runnig in the roundpen or is standing in a halter. She WILL have to move her bum away from you.