Whatever I end up going with I'm certain she'll be thrilled with it, (So will whatever fish that ends up in there as she spoils her fish more than anyone I've ever met)
i learned something very valuable today... i will never again recommend or support an oscar in a 55 gallon tank.
i just measured mine with a tape measure. the interior width of a standard 55 gallon tank is 11 3/4". that means an average to small oscar COULD NOT TURN AROUND with out touching the tank.
COULD NOT TURN AROUND. wow, thats some hard hitting knowledge.
i would say that three or four firemouth cichlids would be nice... you might have to exchange for aggression, and maybe all females might be the way to go, but they max out at less than six inches. you might even get some viable fry out of it. ive also heard that two or three males wont kill eachother if there is no female present and adequate space.
they have a nice pink belly too (or is that kribs... get them messed up).
edit: re: oscar size.. meant average to large, but a 12 inch healthy adult is average to small.