There is a lot not being said.
For some reason the medical staff believe the best outcome will be achieved in a London hospital. That 'best outcome' will be a baby and mother who are both alive.
I grew up with an acrophobic (also alcoholic) mother and it is more complicated than not leaving home / safe space.
I am thinking about my mother here, but is she was told, "you have to go to the hospital now", even for life saving treatment, her mind would lock on to 'leaving safe space' and she would do anything to stay safe.
On the other hand knowing you have to leave at a date in the future things can be planned, how to travel there, what things to take, what will happen when you get there etc.
I'm trying to think of an analogy, maybe this. You are at the top of a 20 storey building and you are told to jump and that someone will catch you, just trust that this will happen - who is going to do that?
On the other hand if you are taken to the same rooftop and told, "in 2 months you will jump and someone will catch you", in that 2 months you go back to that roof and see that there is someone to catch you, that that person is an expert and is wearing a safety harness. You will get your own safety harness, there will be a cushion underneath both of you and another person can jump with you, it will still be a hard thing to do but would you jump?
Hopefully she will receive support towards this.