To the OP: Yes, of course she has a choice, but there is not a lot that you can do about it though. You would be putting a wedge between the fiancée and bride to be. You can offer to be supportive, and be an ear if she needs one. You can offer advice, but ultimately you are not in control of their family. If they are both young, then he is probably listening to the influence of his parents, and she is marrying into that family.
I really do appreciate your concerns. I prefer to eat healthy, live healthy and use natural remedies. That being said, if I get hit by a bus, don't give me eucalyptus oil, take me to a hospital. Kid has strep, give an antibiotic. I disapprove of the notion that you aren't Trad enough if you don't reject modern medicine. Not all doctors are evil, not all modern medicine is bad. Hospitals have their place. There have been many comments I have heard in the past by Trad parishioners medical related issues that it makes me feel bad for their children. I remember one mother that had a young daughter with untreated epilepsy because they didn't want to give their daughter drugs. "Drugs are designed to kill people." I remember a parishioner tell that same mother that the next time +Williamson was coming to request an exorcism. +Williamson had apparently cured it once before through an exorcism at a baptism. Or there was a family that had two cases of mumps. They brought their child with mumps to Mass (on two different occasions) because they didn't believe in vaccinations. In fairness I'm sure they didn't know it was mumps before they came to Mass with a sick child, but the principle remains.
All that being said, there are a lot of great things that midwives are able to do, and I will always speak highly of them. You friend will be ok, and if not the midwife will make a recommendation. Midwife services are far cheaper than a hospital. The lovely lady we used identified a health concern with our third and wife had a emergency C-section. Everyone is fine, healthy and happy now. Either way praying for a healthy child.