IMO (and mind you, I'm not a parent) you have every right to apply the authority of parenthood to argue strenuously for *your own* position, whatever that might be - with the final choice remaining with her. Did you do that?
My sister had a kid at the age of 14. I would not want to be without my nephews now, but when I see the wreckage of my sister's life, I can only wonder if alternatives were discussed back then, and whether or not my parents shirked some of their responsibility in the matter. Am I arguing that an abortion in a 14 year old would have been the right thing to do? In a sense, yes - of course in hindsight it's sort of a meaningless argument. My nephews are here, and what's done is done.