Don't assume so much. Sounds to me like she was raped and chose to have the child anyway.
I shouldn't assume you say. Your argument is based on your own, different, assumption. That's hilarious.
Father's mistake could mean anything - like dumping her when she told him he was pregnant, like declaring that he's not cut out to be a father, like declaring that he's going back to his wife and kids and doesn't want to see the mother or child at all.
If she was raped, then keeping the child is out of the ordinary. She asked what people thought about single mothers. Most people don't think single mothers are pregnant because they were raped and are carrying the child to term.
Regardless of the circumstances, my closing argument remains, the child inherits behavior from his father even if the father is not there raising the child. If the mother has had a difficult time dealing with the behavior of the father, then she's likely to encounter the very same behavior in the child as the child matures.