If Someone Is a Dormant Carrier of Cystic Fibrosis, What Are There Symptoms (If Any) and How Is It Passed On?

My sister found out she has cystic fibrosis today. She said that she found out she has a portion of it and if her boyfriend has it too then there soon to be baby may have it. She wont stop crying and I want to know if this is that serious… and since she only has a dormant portion of the disease and its genetic.. if her or I could be affected by it’s symptoms. Thanks for your help I truely appreciate it.