Whether its sensible or not it is her right and legally in the UK the fetus has no rights.
There have been cases where drs have tried to go to court of get a fixed c section etc and they have been refused. They can only apply on the grounds that the mother is not in a fit mental state to make a rational choice.
The midwives and drs wouldn't be sued, they would make sure she was making an informed consent, you would have to sign to say you are making your choice against medical advice etc.
And a woman cannot be jailed in the UK for refusing medical assistance that would have saved her baby. In the USA yes you can, but you can also be arrested for buying alcohol when pregnant in some states.
Research the legal side of it, there was a case where a woman was actually falsely held and they were trying to get a court order to do a c section,the court of appeal upheld that try fetus has no legal rights and women have the right to bodily autonomy. This was in the UK and there is an aims report on it.
Morallya and ethically we may think the fetus has a rights and a woman has some sort of obligation towards the fetus but legally it has no rights until born.
As I said it may be unpalatable but that is how the law stands and is as it should be.