I don't want my SIL to be our surrogate

Long story short, my SIL recently had a baby, and I guess she is strapped for cash and has baby fever again or something, she told my husband (her step brother) that she was thinking of becoming a surrogate to make more money, and that my FIL told her we were thinking about surrogacy. I have medical issues that make it extremely high risk to carry a child physically, so we have been talking about gestational surrogacy (our egg and sperm, no donor) or adoption. She is currently in a TERRIBLE living situation and makes poor life choices overall, including drinking and smoking marijuana while pregnant with the child she just had. I told my husband I am really not comfortable with that and if we go that route I wouldn't want her to be it. He said he understands but I can tell he is kinda salty about it. He always gets defensive when I talk about her lifestyle and poor decision making, but I have this weird feeling that he wants her to be the surrogate just to not hurt her feelings if we pick someone else, and it's making me really nervous. Just wanted to get that off my chest.