Oh, she is such a cutie, raptors!
When you took her to the second vet, did you show him these pictures?
Has she been under any unusual stress in the past few months? I'm assuming that they checked for corneal problems or something stuck in the eye and came up with nothing?
It looks very similar to our cat's eye problem, but that probably isn't much help since we haven't found anything to fix it, either. JD has had occasional flares of what the vets are assuming is feline herpes virus--his eyes water, he squints and the lids puff up, and he might get some crusty matter that I have to clean off. Herpes in cats is apparently a funny thing--they can usually keep it suppressed, but in some cases, it becomes chronically symptomatic, like in JD.
L-lysine was suggested both by our vets and by people I know, but it didn't seem to do much for JD, and it upset his stomach, so we discontinued it. It does work for some cats, though, so it might be worth a try.
I've discovered some other things that have helped, but not totally eliminated the eye irritation. Once or twice a day, I'll wipe the affected eye(s) off with a bit of clean, cool damp cloth or paper towel. If there's matter buildup, I'll soak the gluck off the eyelid. Believe it or not, the eye treatment that works the best is tears--real, human tears. I discovered it after one of our dogs passed. I was cuddling with the cat and crying and his eye needed cleaning, so I used my tears to clean his eye.
I just grabbed some liquid on a finger and used it to clean away the residue on his face. It worked great and the eye went back to normal for a few days! Weird, but it is what it is.
I don't know if it helped, but we switched him off kibble to a combination of high-quality canned and raw food, so that might be something to try, as well, if she's on a dry diet.
It seems better some times of the year--and I'm wondering if it has something to do with humidity. When his living area is less humid--in summer when the AC is on or in winter when the furnace is running--his eye seems better.
So controlling the humidity may help...
But as I said, we really have no clue and just try to notice what things help and what things have no effect. The good news is that he got better as he got older and in better health. (He came as a very stressed stray 3+ years ago and it took him a while to get better.)
Good luck with your little girl! Please keep us posted. And we'd love to see pics of
both your kitties!