What the fuck is wrong with him

Female cat aggressive after spay surgery

We got our cat Peppa spayed and everything went great, she was in a calm safe room to recover for a slightly over a week. Her incision was looking healed and we decided it’s time to let her out to begin normal life again. Unfortunately, she has begun violently attacking one of our other cats. We have a big house/big pack of kitties and everything always ran smoothly before this. I should mention that Peppa is 12 pounds and the cat she is targeting is slightly over 20 pounds and male. Every other cat in the house is also spayed/neutered. Chico (big guy) is not going near her or instigating anything, and even rolled over on his belly to show submission but she still attacks. We don’t want to keep her separated as she’s getting stir crazy and lonely, but what can we do? We’ve tried trading their scents, catnip, silvervine, and they all have separate food and water and plenty of space to roam. Only other detail I feel like *could* be relevant is Chico had extreme ear infections when he was younger and now has permanently folded ears. Maybe to her it looks like an aggressive expression (like cats fold ears back when angry?) however these two have lived together for almost 3 years. She even sits outside the room he’s in and growls. Any advice would be incredibly appreciated.

What is this bump?

What is this stange bump on my cat's neck?