If CeCeilia is that aggressive, there are very few other fish you can put in with her. I used to have 2 oscars - and I had a Geophagus acuticeps in with them - the pet shop called him a "Gravel Eater"... He nosed around the bottom of the tank, picking up the gravel in his mouth, rolling it around for food bits, and spitting it back out

If you do get one - be sure to get one that is about the same size or larger than CeCelia.

Here's a link to check out the fish itself.

Geophagus acuticeps