My sister can't conceive. I've told her I'll be her surrogate.

My sister is about 36 years old. Been married for 14 years and hasn't not been able to have a child. Her husband has a 17 year old daughter so he's not the problem. They've both been checked and it's her having the issues :( she had in vitro done but no success...I told her I'm willing to do it. I have a 2 and a half year old daughter. I would love nothing more than for her to experience motherhood. I think she's hesitates because she's afraid I might not want to give the baby up and all that legal matter. I would never do that though. Maybe she thinks I'll get attached idk. She wants to try one more time...we live in Southern California. I wanted to ask if any of you know of a reputable Dr that does these treatments.