I doubt your paradise fish will allow much of anything else in her tank. They are one of the most aggressive freshwater fish available. How did you decide to get one of those? I've had one, loved him, but couldn't put anything with him except 5 Badis Badis....and that was in a 30 gallon tank. He seemed to (barely) tolerate them because they were so small. At first he tolerated 3 Bolivian Rams, seemingly because they were bottom-dwellers and he maintained mostly the middle and top, but once he matured a bit he began picking on them...and anything else, except those tiny Badis Badis.
You managed to get just about the most aggressive fish you could find, so I doubt you'll find much that will co-exist with a paradise fish, especially when she's mature. And absolutely do not try anything in the same family, like a gourami. You'll wake up to a dead gourami. The paradise fish will always win... The paradise fish is beautiful and full of personality, why not consider keeping the single fish? It's a small tank and she'll get nearly as big as your hand if fed a varied, healthy diet twice a day.