in a 55? man i dunno....its really not a good idea. try a few jewels, cons, a pike species that stays medium sized, some medium really tough guys who wont grow large. some people have to learn for themselves and i understand that i don't like taking advice if i don't respect the person. so my only tips, as it seems you will try it is 1) try another species of fish eg. a birchir, catfish, loaches/botia or knife. all of those will/may eventually need a bigger tank tho. 2) get cichlids that are tough and max out at about 4" - 6" keep about 4 to spread her aggression out a bit. 3) get another really tough SOB fish with a completely different body type. In reality 55 is really only good for her tho.