Does it usually heal up pretty good? Should I do anything out of the norm to promote healing?
I'm really glad she is still eating well, makes me confident she is still ok.
Have you tested the water for ammonia and nitrate? Keep the water very clean. Salt will help but it will heal without it also. That's assuming it is an abrasion. I'd move the pleco asap. If it's internal, you need to change things up. My ray had a fading color skin issue like this that I believe was occurring because of lack of nutrition and varied diet since it only ate one thing. It healed by varying the diet and feeding more. What's yours eating?