If someone please give me answers, please because I am worry this will affect my sisters lifespan by reading on google about this?

My sister has cystic fibrosis but the rarest one that there's only one other person at there like her, she was in and out of the hospital from a bad stomach virus and when they check the cystic fibrosis it was low (I believe my mom said it was like if it wasn't there), I never google about this but when I did I saw it's a short life span you have when having this, I got so scared and depressed. My sister acts like a normal happy kid she is 7 and we found this out when she was a baby......please does anyone know like would she have a normal life span and will live long? It won't affect her? I believe doctor said she will have a normal lifespan or a long one