I can't tell which it is from the pic, but she now obviously has some kind of secondary infection - either bacterial or fungal. If you are treating with anti-biotics and not seeing any improvement (it seems to have gotten worse as far as those spots go), try some anti-fungus meds. Make sure you do a big water change before you start the new treatment but also do regular water changes afterwards - it realy, realy helps. I wouldn't euthanise her now. If the disease has not killed her yet and she's still eating, she still has a good chance of recovering fully.