She's fully grown now as far as I know, about 4" long. As for fish, I had one in another tank that I housed some mbuna in overnight. The mbuna had lobster tail for dinner. Don't mix with cichlids. I dropped a couple BN juvies into the tank with this one; they disappeared rather quickly. I didn't see too many Endler's disappear when they were kept together, but with Endler's it's hard to tell anyway. They breed and move around too much to keep a halfway decent count.
She'd really be best in her own tank so the babies won't get picked off when she breeds. I'm not sure how often she'll breed, it also depends on temp and feeding. She has produced one clutch so far, but I didn't see any babies so I presume the Endler's picked them off while they were tiny.