Hello there, and a thousand thanks once again for all the really useful responses you have given, both positive and negative. Happily, my friend says that she would appreciate it if I would post on her behalf. I'll try not to go into too much detail, but for some reason I can never get my posts in under 1,000 words, so forgive me for that!
I will declare up front that, like the rest of her close friends, I think she should go ahead with her pregnancy. But she's the one that will have to do it and only she can decide.
She is in early 40s, as I say, and given her circumstances if she terminates this pregnancy it is highly unlikely she will ever have a child. Father ended what she thought was incipient relationship the second the deed had been done (before even she knew she was pregnant) - three cheers for him, then.
Here's where it gets very complicated. She is totally on her own, in that she has had no contact with her parents for many years, and virtually none with siblings (I don't know the full story, but there was clearly some significant emotional abuse). Her childhood left her with very low self-esteem and she has spent a long time dealing with clinical depression (very extreme at times). She has been on anti-depressants for quite a while and they seem to have helped, but as far as I can see she is rather stubborn about wanting to wean herself off them and that has caused relapses. Also, since she separated about 9 years ago from a partner of well over a decade, she has had a small number of relationships with men who have all screwed her over badly. She thinks it's her fault, whereas I think it's just horrible luck. She also thinks that her failed relationships are some kind of evidence that she will screw up a relationship with her child (I totally disagree with this as I am hardly a shining example of successful marriage myself and yet I think I am a fantastic mum!)
If she terminates, it won't be the first time. She says she never really recovered from having to do it once a long time ago. Does she want a baby? She says she would have been thrilled if the father had stood by her. Bringing a child up on her own fills her with panic, but so does the thought of a termination.
She has what seems to me to be a large number of extremely close friends, in the UK and elsewhere, who are all pulling to support her. We all think she is the bee's knees - really attractive, highly cultured, dead intelligent, but she has been depressed for so long that she just can't believe us. And highly unfortunately, she moved overseas last year, away from all her friends and into an extremely stressful job. She has been working 7 days a week for ages (I worked for the same employer and know they simply expect that - you get no credit at all). If she does go ahead with the pregnancy, I can't see that she can possibly avoid moving back to the UK where she has a support network, and I think she probably sees that.
On the financial front, she is earning pretty well now, but has been so unhappy in her career for so long that we all want her to find something that will make her happy, or at least be a neutral factor instead of aggravating her depression. Easier said than done of course - and she has a lot of fears about just chucking it all in and hoping for the best. (I myself think that if she goes ahead with the pregnancy, she should allow herself some down time. Even though it will come at a cost, she is easily good enough to get back onto the treadmill.) She does have a flat with not much of a mortgage left on it back in the UK, which is great news.
I have loads more thoughts about her situation, of which she is well aware. Most importantly, I am not alone among her friends in thinking that a child could give her an emotional anchor - a meaning to her life (though of course she is terrified she will damage him/her). I also think that she would need to be very determined about managing her depression and not ignoring what the doctor tells her. And finally, I agree with many of you that it's better for a child never to have known a parent than to lose one under ugly circumstances at an early age.
But that said, I would appreciate it if you could all give her your thoughts given your own experiences of being single mums. I do hope that I have represented her situation here accurately, and that she will chip in to clarify anything I have got wrong.
Thank you all so much.