On Chicago Med (A US hospital drama, bit like a soap really) they showed what can happen in emergency medical situations. I'd read the appalling US surrogacy contracts before, but this was actually how one would be implemented.
Surrogate presents to hospital with asthma, five months or so pregnant with twins. Intended parents turn up. Scan reveals one twin has severe problems that if untreated may eventually kill other twin too. Doctors say can either wait and see but may lose both twins, or selective reduction.
Surrogate wants to wait and see. Intended parents want selective reduction. Dr says that the surrogate is the patient, it's her choice. IP get their lawyer into the hospital room of a sick pregnant woman and threaten all sorts of legal action and tries to bypass her wishes by going to the hospital's legal team. Surrogate is terrified as she can't afford to pay back all her expenses and the cost of the IVF.
It all got resolved perfectly amicably in the end with the surrogate putting her life on the line going through an experimental treatment to try and save both twins. Being TV of course it worked and everyone was happy.
DH and I haven't been able to have children. Under no circumstances would I pay to have another woman go through it and buy the child: I often see people saying that until you've been through infertility you don't know you wouldn't. Well, I've been there and I wouldn't.
I can just about get my head around altruistic surrogacy - so for your sister, cousin - but even that I'd probably ban if I could. If that does remain legal, I do think it should be tightened up so that only those with a link to the parents can become a surrogate, not just finding them on Facebook.