Firstly - look at her rump, does she have any form of horizontal rub line across her butt below the top of her tail? If so, then the lice are still there.
Secondly - bacon grease?? As in extremely salty fat? If she's being rubbed under the saddle that bad then the saddle really isn't fitting. If it's rubbed sore then salty bacon fat is going to sting! Ouch. She shouldn't be wearing any saddle at all until the sore spot is completely healed. Treat the rubbed area with something designed for skin like diaper cream and keep the saddle and the pad off until it's healed. Then I think you need to have a look at the saddle fit.