Tell her she can't introduce a new clown with an old clown and expect them to not fight!
It'sfine to put an injured fish in the QT
. It's a good place for him to recouperate without the possibility of harassment by other tank inhabitants, if he's injured he may be vulnerable. Melafix can be used in saltwater but you need to make sure you don't overdose. I would definately put him in QT
if you're going to try the melafix and not put the melafix in the main tank. I believe that damaged fins, etc. can make him vulnerable to secondary infections, but I'm no expert, this is just what I've been told by the experts.