I rehomed 2 cats a month ago. Assumed that cuz they came together, they would get on like a house on fire! They fight on a daily basis, Peanut sounds like she's being murdered most of the time, growling, hissing, yowling etc...
I recently found a cut above Cooper's eye where Peanut obviously got her own back
I was worried sick to begin with, but I let them get on with it because neither of them are showing signs of stress or submissive behaviour.. I have now started to witness moments of niceness towards each other...Peanut will wash Coopers face.
They never sleep together, I will usually find them at opposite end of the room!
I really hope the situation calms down for your pair....its not nice to watch, especially when its mother and son.
Good luck with the Feliway (should you try it..)