I'm currently pregnant (2nd trimester) with a boy. Seeing as I have a reduced work pensum due to health reasons... Well, let's just say I have too much time / had the time to think quite a lot about this question.
How I would like to react:
I think I'd try to be truly neutral as long as I felt like my DD could live with the options/see them through.
Talk about the imo possible consequences for each option and probably book her a counselling session ASAP. I believe that this would have to be her choice and a choice she could also live with (from an emotional but also a realistic point of view)!
And not informing her of her choices / not making it clear that every woman has a choice (should have a choice) would be coercive as well.
But I would also try to be honest. Could we (DH and I) support her? Would we have the finances? The time?
This imaginary DD might have a sibling with special needs
Or one of her parents (DH or I) could have had an accident or an illness related disability.
I feel like I would try to be supportive (yes, of all options).
But I also feel like this baby could and should not trump the welfare of other family members (which includes myself, btw). Especially not in the case of this DD having siblings...
If DD wanted to keep the child, she'd need to be the mother. Do late night feeds, sacrifice things like going out, having time consuming hobbies etc... I would be supportive (how supportive would depend on the circumstances) but that child would be her responsibility.
And she would also need to be able to come up with a plan in regards to education, her finances, the father etc. Not that I wouldn't support her in this process but she'd have to show willingness and maturity.
I truly don't know what I'd do if I felt like DD simply couldn't handle that responsibility or wasn't willing to shoulder it. Certainly not force an abortion but it would make this situation much more difficult and immensely complicated.