My girlfriend was diagnosed type 1 diabetes when she was 12 yrs old, nw shes 23 & jst now she was diagnosed with stargardt's, how can she be fine :'(?

Can be both: Stargardt's is inherited as a type of macular degeneration and visual loss often comes in her early 20s. This is something that she needs to discuss with you and with her physician to help clarify how the diagnosis is made as it is inherited and it is rare. There are some investigative studies that are in the process now. You can ask your opthalmologist.