I don’t know how to answer this–it’s a situation that just doesn’t come up much in my life. Maybe I’m not social enough.
Two experiences spring to mind:
The first was my step-daughter, who found herself pregnant and single. Being anti-abortion (I guess I did something right) she insisted on having the child. We tried to convince her to give him up for adoption, but she was unwilling. My spouse and I raised him for his forst 2 years until she got her life into some sort of order that would allow her to take him.
The second event was a very close friend of mine who in her 30’s who, despite being a virgin, was terribly concerned that she might be pregnant. I spent that conversation trying (unsucessfully) to convince her that aborton was not an answer. As luck would have it, though, it turned out to be a false alarm. She still complains to this day, however, that I was more concerned about the (potential) baby than her.
(A non-experience occurred when I lived in Texas. There was a (non-Catholic) church-related ministry that would place unwed (teen) mothers in volunteer homes if they were kicked-out by their parents. We volunteered, but because we had a teen-aged boy living in the house at the time, we weren’t allowed to do so.)
So, lacking sufficient real experience in the situatuion you describe, I have to say I honestly don’t know how I would react, but I do hope it would be with charity.