Weird third eyelid

My Ivy's behaviour, eating habits, etc have not changed at all. But last night I was in the kitchen and as she looked up at me the light caught her eye so I could see that weird shiny night vision thing that cats have. She looked like she had something on her eye. So I had a good look and there is something clear on her eye, and the edge of the white third eye lid looks jagged - like a bit broke off and is floating around Ivy's eyeball ... it doesn't appear to be bothering her, but I don't want it to get bad/worse ...

I'd recommend at least a phone call to your vet. They will probably need to see your kitty for themselves.