We Need Behavioral Help
TL:DR My traumatized angel baby cat likes to harass the elderly and it's getting out of hand.
Last October, I (27F) left an abusive relationship, but I couldn't take my cat. After a month and a half and a whole legal process, I was able to get my baby girl Glen (2F) back, but she's had a hard time getting along with my parent's cats (Melody and River, both 14F).
My ex (26F) and I adopted Glen (three-quarters persian tortie) when she was 8 weeks old. We already had two other cats (a middle-aged persian and a 1 year old shelter mutt) and we lived in a one-bedroom apartment. A beagle puppy got thrown into the mix and, after the persian died unexpectedly, we almost immediately got two persian kittens. This was all in a one-bedroom apartment. I know that it was basically a hoarding situation. The reason I left the relationship was that she was going to get another puppy. There were way too many animals in that apartment.
My ex was verbally, emotionally, and physically abusive. There would be shouting matches at least twice a week, which would often escalate into violence. My ex was also mentally ill and untreated, so there was that chaos as well. Glen is my cat, she has always been bonded to me, and we had agreed that if we split up, I would take her. When the break up actually happened, though, my ex hid Glen and filed a restraining order against me. I got her back a month and a half later.
I don't know what happened during that month and a half. I think she was moved to my ex's mom's house, locked in a room (her mom has an antisocial cat) and ignored the entire time. I think she only had her siblings for comfort. Glen has historically been a prosocial cat. She was particularly close to her older sister and one of the kittens. My sister thinks that Glen was physically abused at some point because she now flinches around rapid movements. When I got her back, she was matted (I'll include a photo of her deshedding) and incredibly clingy. Whenever I'm home, Glen is nearby. If I don't come home on time, she gets upset. For a few months after she came home she would come when called by name with perfect recall.
My parents cats don't even like each other that much and they're bonded sisters. They're also definately getting older. Both of them HATE Glen. During introductions, Glen would try to play with them and they would rebuff her every time. We tried distracting them, playing with them, giving extra attention, and feeding special treats while in proximity of each other. Nothing improved. One cat hid for days on end and the other ended up breaking out into hives. Eventually, we decided to keep them separated.
Glen now regularly growls at and charges the doors to rooms the other cats are in. There's now been one proper fight when Glen bolted through an open door and another very close call. She seems to be escalating.
I think that Glen is anxious, frustrated, and bored. She has all the toys a cat could want (I work at PetSmart, I would know), regular human attention, a room with her own food and water, multiple scratching posts and beds, and a cat tree. She's also harness trained and I've taken her outside. I think another part of the problem may be that my parents cats are indoor-outdoor and Glen can see them outside (Glen will be an outdoor cat over my bleeding corpse).
My only idea at this point would be to get Glen a kitten so she has something to do besides torment the elderly all day, but I know that also comes with a new bucket of potential problems. We're at our wit's end and things just can't stay like this. Someone's gonna get hurt. Thank you for reading my small novel and I welcome any and all advice people may have.