Redish eye with clear tears/pus? Please help...food allergy???

I came home from a night away and my cat has a redish eye and there's a clear pus or tears coming out of it. Pics at the bottom of the post.

I don't think it looks terrible but I really need suggestions for home remedies because I'm really financially struggling lately and a vet visit is expensive. 

Anyway, the only new thing in the past 2 days is that I have been putting some new food in her bowl mixed with her normal food. Not much at all, just to get her used to it. I suppose it could be an allergy maybe?

It also doesn't look swollen but a little puffy.  I've only been home for 10 mins as I write this so I'm gonna keep watch on her and see if anything changes or there's anything else. She has her normal energy level and is acting normally.

Could I give her eye drops or should I wait a bit and see if it gets better? When should I take her to a vet if it doesn't get better?

Thank you!!

The second pic is just her closing her eye its not swollen as much as it looks in that pic...

She needs a vet.. Eye issues can really go bad very fast. She needs to see the Vet.. sorry...if it gets severe enough, she could lose vision in that eye. 

I did not know that, until last year, when my guy had a small scratch on his cornea. The Vet verified that it eye issues can change dramatically bad, very fast. 

She is so pretty!