What principles should inform her choice?
We are forgetting about his choice. I'd wait until the child is born and then get a paternity test. The other is the circumstances. I'm assuming she was using birth control. If she was on the pill, most likely she got pregnant on purpose to lock him down, in which case she is a liar, beyond the fibs that most women tell.
There are two choices, based on the kid, because he is the only one to consider in this scenario:
1. Assuming this was on the up-and-up, and they were talking marriage anyway, marriage is the best route. The kid gets a father.
2. Put the baby up for adoption. The kid gets a father.
Jaded much? It sounds like they were in a relationship that was committed enough that I don't think he would need to worry about a paternity test. Secondly, "got pregnant on purpose?" Do you know how often condoms and pills fail? All the time. Do you honestly think most American women aren't on birth control or using condoms? They are, but these methods fail all the time, hence the large number of abortions.
Also, do not assume she was using anything. If these intimate encounters were not premeditated, but simply fallen into b/c of a lack of self control/parental supervision/good chaperoning/etc, then neither the man or women would have been "prepared" in that way. I know couples who struggled to stay chaste in unguarded relationships. They did not run out and buy a bunch of birth control b/c every time they fell they would be really sorry and regretful, and try hard never to do it again. To buy condoms and keep them handy would be to willingly give in to future sin.
