would be be a surrogate mother?

My sister got the news she couldn't have babies due to her medical condition, her husband and her are in so much pain. She asked me to be her surrogate since Im the only one who has had a baby. I really want to help her out and give her the child she wants, but I'm extremely scared of caring a baby for 9 months, giving birth then getting attached. What would you do? What if the possibility of me getting attached to the baby?