Cat with weeping skin.

I have a young cat (about a year and a half) that I found (and finally managed to catch) in my neighborhood about 7 months ago. Someone had put a flea collar on her, and she had managed to get her left front paw through the collar........so that the collar ended up around her neck and up under her shoulder. She was like that for maybe 3 months (I know because I was actively trying to catch her) and as a result the skin in her "armpit" was literally worn away. When I caught her, I of course took her to the vet repeatedly for treatments (antibiotics, deworming, cleaning the wound, etc.). The area has "healed" and no longer seems to bother the cat, but it seems to sweat and the hair around it mats........so I try to keep it clean and trim the hair back. But the area seems totally devoid of any skin. It's not an open wound obviously, just very pink.......it looks like just the slightest transparent covering over meat.....just like there is no skin whatsoever. The cat seems to be just fine in all respects, but I worry about that area. Is there anything else that can be done? A surgery perhaps. Or am I worrying needlessly and the area will eventually develop a more substantial "covering"? The vet she saw basically said (when she was been treated for an actual wound) to just wait and see. I've spend a great deal on this animal and am certainly willing to spend more, but I would like your opinion. Thanks very much.