How to stop pearlscale goldfish from bullying other goldfish?

I have two pearlscale goldfish(one with a wen) and one telescope eyed goldfish. All are relatively small but one(Bessy) is bigger than the other two. The tele-eyed one is new to the tank. The tank is only 30 gallons(larger tank sprung a leak and is having to be repaired). They have been in there for a few weeks now and I noticed smaller crowned(wen) pearlscales back fins look kind of nipped(his fins hang down and fold into itself like a large scarf so it's kind of hard to tell but when I put the new guy in there I noticed over night his fins ripped at. I was housing a friend's betta until he got his tank cycled and thought the betta was the culprit and removed him to quarantine but I noticed Bessy chasing both other fish around and she is bigger than the others. I tried rearranging tank but that doesn't seem to stop her(not sure if actually female). She gets really aggressive at feeding time. She did the chasing think some in the larger tank but I think it's gotten worse since the move. Is there anything I can do or do I need to get rid of her? She's very pretty and wasn't cheap but she's nipping the fins off other fish.