As long as you build a good trusting relationship with her, and start slow so she can get used to what you are asking her to do, I don't know why you can't. Since she's been blind in that eye most of her life, its not a new sudden thing that she has to get used to, and obviously she's learned to cope well enough on her own, so as long as she feels comfortable, I say go for it. John Lyon's horse Zip lost the sight in both of his eyes after an allergic reaction to a drug, and John still used him as his clinic horse, and still went out and worked him over all sorts of stuff. Because the horse trusted the rider, Zip was willing to trust the John wouldn't let him get hurt, or put him in a dangerous situation. Post pictures if you can, I'd love to see your horse.