What can I do to stop my mom from breeding her dogs?

My mom wants to breed her AKC German Shepherd because she said that she tested negative on all the tests.(I don't remember what tests got done)I told her its not a good idea.I know her Shepherd has excellent bloodlines and my mom wants me to show her Shepherd for her but I really can't stand that dog.She also wants to breed her Bull mastiff when she's old enough.Her Bull mastiff isn't AKC registered because the breeder we got her from didn't register her.I know I bred my Scottish Terriers but that in a way was an accident.