Just rescued this poor baby

Hi, so i dont usually post on forums but this is new to me.
A little background, I have owned 2 chins in the past, but neither of them ever got sick or matted so im new to the whole health and hygiene issues.
I rescued this 1 year old female chin on Monday from a girl that was selling a "cage" online and told me when i went to pick it up that shes giving me the chin too.... ohkayyy i thought no big deal, i go see her and one of her eyes had a hugeee red bump near it (near the tearduct) her eye was completely crusted shut and her ears are dry and peeling, as well as her feet her fur is terribly matted and this girl refused to bring her to the vet or anything.
I decide okay fine ill see if i can help this baby, scoop her up and the lady gave me the chin and everything for free so I took her straight to the vet, vet didnt say what it could be but we settled with antibiotic injections 1x a day for 10 days.
We got her eye cleaned up and by nighttime it was crusted shut again. I dont want to stress this poor baby out too much by cleaning her eye 3x a day and trying to get her fur back to normal but I desprately want to see her move around normally (since practically her whole underside is matted and crusted with urine)

How can I go about getting these huge mats out? ive gotten most of the ones on the top out, but am really struggling with her whole underside and I dont want to ruin any chance of gaining her trust.
Is there anything I can put on her ears and feet to help with the dryness?

So sorry for the huge scrambled rant, I just still cant believe the shape she is in. She also seems really underweight, i can feel every rib and bone perfectly.. as if shes literally just skin, bones and fur.

Any advice is greatly appreciated, and ill post a couple pictures later.

For the mats, I would try a to comb and pull them out. Start from one edge and work at it, but try to gauge her stress and do it over the course of days. You can try to clean up some of the pee with unscented organic baby wipes. Unfortunately at this point I think you need to worry about getting her healthy and comfortable and then work on building trust.

For her ears and feet the best thing is bag balm, but if you don't have any vitamin E liquid caplets can work, just poke it with a pin and squeeze it out. With both of those things though, a little goes a long way so be careful or you will have a greasy chin.