My 10" texas male is a bully as well; just the texas nature not much you can do about it. They tend to always chase fish around, but aren't big into actually beating them to a pulp. And to the poster that aquired about it being a hybrid, it looks 100% cyano to me.
You might try the dither approach, but I doubt it will solve it completely; it'll just give her more to chase around! As far as how many, you could do 5 or 6 silvers in a tank that size. red hooks are a bit harder to find, but I'm sure you could do a few of those as well. Tiger barbs I do not suggest, cause if the jack is a bit stressed out, they are notorios fin nippers, and might do more damage to her.. Other kinds of barbs do well also, just steer away from the prettier, more expensive ones! Dithers are always expiremental and and I do not suggest ringing up a decent bill on them!
Good luck with everything though. Your fish look nice and healthy and seem to have a very caring owner..