My son is also 4yo and I know my stbx is coaching him with the same b.s. During our last visitation he told me "Mom said you lied." Before that he said "Mom said you don't know how to marry." There's plenty more where that came from. It is damaging beyond belief, but her rage and thirst for revenge has blinded her to the effects this is having on our kids. Our 10yo daughter is already confused. She has her convinced I am a pathological liar and the girl refused to talk to me and skipped our visitation this week. Fortunately we were able to have a heart to heart during the return exchange with my son and the nanny the next morning, and she will see her child therapist next week. I think things are better now, but I just keep waiting for the next shoe to drop.