Diabetic dogs often develop cataracts secondary to the diabetes - I am assuming that is why she is going blind (as blindness can be caused by many things). Cataract surgery might be an option if there is a veterinary opthomologist in your area (how close are you to the vet school at LSU?), your dog is a candidate, and you are willing to pursue it. If not, it just depends on how well she adjusts to being a blind dog and what her quality of life is. My parents had a dog that was diabetic and developed cataracts. They attempted surgery but she developed complications and ended up blind anyway. She did ok - she still knew inside vs. outside, she was kept on a leash outside so she didn't wander off, and she was familiar enough with the layout of the house that she didn't usually bump into stuff (my parents made sure they didn't move any furniture around and that she didn't have access to the stairs. But she was also a older, small-breed dog that spend most of her time sleeping on the couch. If you had a dog that was really active and really depended on their sight to enjoy their life and do the things they loved, like running chasing balls and fetching sticks and such, and/or started developing anxiety issues from not being able to see, I could see where their quality of life is not what it should be, and then euthanasia could be considered. It all just depends on how well they adapt - many dogs can, but not all. I think it also makes a difference if they lost their sight gradually and have time to adjust, vs. losing it suddenly all at once.
I know it's a really difficult decision, but if you feel in your heart that this isn't a good life for her, having her put to sleep would be the kindest thing you could do. I always try to give people options as far as their pets' treatments and health care, and then decide what they feel they can handle, and what is in the best interest of the pet. That's going to be different for everyone because of their pet as an individual and what they feel up to managing. I have euthanized diabetic pets when they have been diagnosed because the owners were very truthful and honest that they were not going to be committed enough to manage their pets' condition - the shots, the medications, the follow-ups and recheck visits, monitoring, etc. I have euthanized cats that are diagnosed with problems that would require them to get a pill given to them every day, when they were cats that were impossible to give a pill to. It's always the owner's decision, with their consent, not mine, because they know what they can handle and what they cannot. And I would rather put an animal down with a chronic disease, if that disease cannot or will not be controlled, than have that animal suffer through the complications that will happen from not having it properly managed.
Good luck with whatever you decide, I am sorry you are going through this. And whatever you do, don't let anyone guilt you into feeling bad about whichever decision you make. You need to do what you feel is best for your pet, and for your family.