I have several maine coon cats one of whom is sickly and mats constantly and quite thickly. He hates to be brushed. Getting the mats out the first time will be the worst then they either need to comb/brush the cat daily or have it clipped (shaved) about twice a year. Whatever you do don't bathe the cat until the mats are out, it will just make them tighter. You can try and work baby or talcum powder into the mats to try and loosen them up, but it sounds like they are too tight for that already. What I did with mine when he got really bad was shave with a clipper blade that was really short (a surgical length blade) little by little. Once you get a mat started it actually is pretty easy to lift the edge and just shave slowly a little at a time remembering to stop when the clipper gets too hot. I had a friend help me because he hates being groomed so much, but surprisingly he didn't mind the clipper. You can try scissors again, but use really little pointy ones and go thru just the edge of the mat with one blade taking just the edge hairs that are caught and cutting very small amounts at a time. If you pull the hair or get too much which causes it to pull you will pull the skin up and risk cutting her again. Mine usually won't stand for much of this. If you can't get the scissors under the edge of the mat you most likely won't have any luck with a mat rake, those pull alot too and still then there's combing to get the broken up mat out. Not an easy situation in any case. You may have to work on it gradually over a period of days, but it would save the trip to the vet, the stress on the cat, and the sedative for her too. Best of luck to you with her and I hope you can help her out, they are painful since they pull the fur and the cat can eventually develop sores under the mats. Some cats can mat very easily so not everyone will think they are neglecting their kitty and at least they are looking to help her. Hope this helps and sorry it's so long....