Abortion and Psychosis, A question

I've a friend, whom I met in hospital, who is allergic to oestrogen. Which is unfortunate because she has XX Chromosomes, as I do. Her reaction to estrogen day to day is severe depressive episodes.
We met in hospital because she'd started taking oestrogen based contraception and it had triggered a suicidal psychosis. If her fiance hadn't unexpectedly come home two hours early to find her unusually calm, she would be dead. That was around 2x her normal day-to-day levels.

This friend is now worried that she's pregnant. Oestrogen levels by the end of pregnancy are, apparently, about 1000x that of day-to-day levels. She's extremely resourceful and, during her psychoses, can be very deceptive about how bad things actually are. At anything more that 2x her normal levels of oestrogen, she will find a way to kill herself.

The Church teaches, through the principle of double effect, that she can continue and increase treatment for her mental illness during pregnancy, even to the detriment of the child. She could take some oestrogen-blocking therapy, even if it kills the child.
The child could, however, survive to or past around 20 weeks when both pain and viability-outside-the-womb become a possibility. If the child is born, at whatever stage after that, there is a high likelihood of terrible suffering for them. It is unlikely that the child will survive long after birth, if at all.

She could, of course, not continue or receive more treatment.

Meanwhile, even a week of high levels of estrogen - much more for if it's 40 weeks - and this friend is likely dead; almost certainly.

Her question to me: How is killing the embryo, foetus, child slowly, possible over 9 or 10 months, more ethical than a direct abortion? My intention in either case is to stop in estrogen and the result in either case is the thing dying?

My question to you: How should I answer?



EDIT to clarify:
 I use allergy somewhat allegorically.
She has BPD and has a psychotic-suicidal reaction to estrogen. 
My assumptions, the 'givens,' are based on my close knowledge of her and her condition.
Also, yes, she could continue with BPD therapy; the resulting death or injuries to the child are of the same likelihood.
And, she uses a utilitarian prism for her moral compass:
"Greatest good for the greatest number," while believing that "There is some suffering worse than death."