What could this be other than pink eye?

I noticed that my dogs eye was irritated. she is great dane/lab mix and already has "sad eyes" her eyelids droop a little and show a little of her red. A few days ago i notice a little red bump on the bottom of her eyelid. I knew another do who had cherry eye and it is not nearly as severe as this nor has it changed. I have also looked at pictures online and the cherry eye pics dont look the same at all. I dont know if she may have a mild case or if it could be something else. Im going to take her to the vet this week but was just wondering if anyone has experienced this or may know something else it might be?!?!