Oh Kim, one more thing. I have read and also discussed with the shelter vet that sometimes leaving the eyeballs in is more painful for the cat than having them removed. If she is not very active then this might be something to take into consideration. I read a particular article about a blind cat that just layed around alot and wasn't very active. The owners finally made a decision to have her eyes removed and they wrote that the difference for that cat was amazing. She immediately became active and healthy. I found out that it is believed by many vets that some cats suffer headaches and pain because of the pressures in the eyes. Even though they can't see and don't seem to be causing any harm they are causing pain. As we all know cats hide pain so well and they learn to live with it. I know this doesn't apply to all cats that are blind and still have their eyes but I thought about it because of all the weeping and drainage. Just something that you might want to discuss with your vet. Some of her weight issues and inactivity could come from pain. Her eyes aren't doing her any good anyway.
It was just a thought that you might want to keep in the back of your mind as you get to know her. It may be something she would need to have done to live a happier life.
I wish I could remember where I found that article!