What Is the Life Expectancy After a Double Lung Transplant if You Have Cystic Fibrosis?

My little sister is a teenager and has Cystic Fibrosis. Her doctor said she will need to have a double lung transplant eventually…her lung function is not good, and she gets frequent infections. She also has a lot of problems with digesting and has to have a feeding tube to provide extra nutrients. I was wondering, does anyone who’s knowledgeable know what the life expectancy is after a double lung transplant considering she has Cystic Fibrosis? And the probability of just surviving the lung transplant surgery?