pleaseresearch,
You don't have to give any details, but I'm willing to say that if your mum has known anyone close to her that was sexually abused as a child in the WTS, and had seen this person/parents told by the WTS/representatives that they were lying, that even if it were true, it is over now and they should forgive to protect the reputation of the WTS (or else), she might finally realize that she cannot be part of an "organization" that allows abuse and protects the abuser.
Sometimes it is not enough to see someone brutally slapped, but when you (or someone you love very much) are slapped brutally, those that see or experience it themselves, have two choices, to protect that person and take a chance that retribution will come on them or to protect themselves. Evidently, your mum hasn't reached that decision point.
Self-protection is a very deep response to danger in humans. The willingness to sacrifice yourself for others, not so much.
Love, Blondie