My cursory look for some evidence suggests single mothers see dramatically elevated rates of violence and abuse. This source surveys children who live with both parents and just one. Children living with just one are seven times as likely to have witnessed someone hitting their mother in the past year than children living with both parents. I take that to mean that the increase in single motherhood means there is more domestic abuse happening than if no such increase had taken place.
Or maybe those women are now single mothers because they were able to escape their abusers. You would have to compare data across decades, and adjust for people being more/less willing to disclose abuse.
https://ifstudies.org/blog/children-in-single-parent-familie...