As I mentioned in earlier posts, I've never had any luck with Melafix.
Please read this short web page. It should help you make a decision.
www.seachem.com/Products/product_pages/ParaGuard.html
It is for everything, especially fin rot, but also cures fungus, bacteria, parasites.
At this point what do you have to loose. She's still sick and new infections keep cropping up. You really need one medication that gets everything at the same time.
Plus if you keep having to mix different meds. your going to need a degree in chemistry. With this med. the chemists at Seachem have done it for you. Just do a a big WC, then add 5ml (capful) for every 10g. It works really well and normally it's quick, but after so much time has passed, it may take more time than usual.
But at least read what it has to say and give it a try. It can't hurt, and considering that what you've been doing hasn't worked, you need to try something different.