Lady has had dry eye for for several years.
It doesn't sound like a tear stimulator was ever prescribed for Maddie. These can help Maddie produce her own tears. Cyclosporin is the old standby, but it didn't work for Lady. Tracrolimus is fairly new and is a miracle for Lady. She started producing her own tears after a year.
Maddie also needs artificial tears 4-6 times a day. Genteal Severe Eye gel is the best I've found.
I would really recommend getting a referral to an ophthalmologist if possible. Dogs with dry eye are prone to ulcers, infections and can build up scar tissue over time which eventually causes blindness.
How old is Maddie? Dry eye/KCS can be genetic in the breed. Some Yorkies can be born without (or very small) glands that produce tears.
KCS (Dry Eye)