So sorry that your young girl has this diagnosis. I know how you feel as I adopted my boy at one year old and at one and a half years old he developed a cataract in one eye. I was shocked as I too did not know it could happen so young. He had uveitis too and that had to be cured first. He saw the eye specialist and had tests to see if he was suitable for surgery and he was.
He did not have diabetes and at 7 years old now the other eye is still ok. The surgery is expensive and the pre and post OP care is tedious and takes some patience and effort on our part with the eye meds etc. They have to wear a cone for a while to protect the eye, but my dog did well with that. The good news is that when the healing was over he can see like a hawk now and is doing fine.
It is important to get an experienced eye specialist vet and really take all the care instructions seriously. The eye meds have to be administered at frequent intervals so someone needs to be there to do this. Cataract surgery in dogs is not the relative walk in the park that it is with most humans. Keeping the dog still and quiet post OP is also important. The reason the surgery is usually advised is the danger of developing glaucoma which can be very painful if not controlled. But your eye vet will explain all that. So all in all, the outcome is well worth it, especially in a young dog.
I also feel for your poor baby who has other health issues too, and for you who is caring so well for her. We do take on a big risk when we adopt pets with unknown ancestry, but knowing we have saved a pet and made them well and happy is so worth it
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So hang in there, and good luck with the eye doc visit. Please keep in touch about how you both are doing.