I'm not sure I like the answer I've given. Issues surrounding girls are more complex, regardless of how complicated or simple any given person may be.
If a boy gets a girl pregnant, it seems to me the questions are straightforward. Will he be an involved father, or not? Will he take responsibility, or not? Will he seek for her to get an abortion, or not? Will he be a good father... That's where things get really complicated.
For a girl, however, there's additional questions. The choice of carrying the child to term is hers, unless nature takes the matter out of her hands. She must navigate for herself the moral and ethical questions surrounding carrying or aborting a fetus, caring for that child, and potentially being supported or abandoned by those who advise her one way or another.
There's sometimes a power imbalance in relationships. This usually favors the male, though less often nowadays. Nevertheless, this means there's more cause for a woman than a man to search for the signs of a potentially abusive relationship. This isn't a question of responsibility, but of stakes.
A miscarriage can be as emotionally traumatic for a loving potential father, but a potential mother who miscarries is absolutely stuck with potential ramifications, and clearing them up or ruling them out.
For boys, violence often is the cause and solution to a problem. Violence is simple, just physics unbottled in the other person's face. For girls, violence is less common.
Obviously this depends on the boy or girl in question. Some girls are violent. Some boys aren't. Some girls have simple troubles, or know how to simplify their lives, while some boys are drama kings who thrive on attention any way they can get it, or perhaps they simply don't know how to navigate social circles.
Nevertheless, I feel that in general the problems of boys are simple but life-threatening, whereas the problems of girls are complex but they are more likely to survive them.
