inner/third eyelid always showing

First of all, I'd like to say thank you for the very warm welcome here. Just recently, i rescued a cat from a very abusive family who threw it around and played with it roughly. It's been two days, and i noticed her third eyelid was constantly showing. From the corner snearest the nose all the way to the center of her eyes. She seems to see things just fine though and eats a lot and drinks a lot but i also noticed that she's not very playful as most kittens should be. Is it something i should be concerned about or is it a normal thing? I'm guessing she's about five to six months old, according to the previous owners who claimed they just picked her up. Thanks in advance for any suggestion/ advice I'll be getting on the matter.

The third eyelid showing is normally a sign that the cat is ill. particularly when she's not as playful as most cats her age would be.  It's definitely NOT normal for it to be showing all the time like that.

Have you taken this kitty in for a Vet visit since you rescued her?  That's a good idea to do, especially since she was abused by her previous owners.  You never know what might be wrong.  Could be something like a small scratch on her eye, or could be something internal since she was "thrown around"..  Hopefully it's nothing too major, but only a Vet will be able to tell you exactly what the issue is.