Seriously sick or just a virus?

For almost a week now, my 11 year old cat, Pepper has not looked well. She has her inner eyelid showing constantly, and her eyes are very runny. She is an indoor/outdoor cat, so I'm not sure if she just caught something outside. I've read a lot about possible respiratory infections or more serious things,so if anyone has any ideas about what it might be, please let me know. I also attached a photo of her eye.

She's probably got a cold or upper respiratory infection. My two just got over it, and I would call it cat flu. One of them was very sick for three weeks. If she gets congested, you can put her in a steamy bathroom several times a day to help break up the congestion. If she starts throwing up, call the vet, who can give you something for the nausea that also clears up a lot of the head congestion. Give her lots of attention and let her sleep as much as she wants.

It's impossible to know whether it's serious or not, or what it IS, but when their third eyelids are showing, it's definitely a sign they aren't well.   Is she still eating?  That's the most important thing right now.  If she stops, and if the steamy bathroom doesn't help, definitely get her in to be seen by a Vet.  But food is her best friend, especially now.  Is she congested?  If so, use warmed up, stinky wet food.