I knew this when the story was that she took a walk with her toddler in the rain at 9:30pm, accepted a ride from a total stranger who punched her so hard, she wasn't able to call police until the next morning.
I am not saying anything, BUT. . .this is a 21 (twenty-one) year old girl who is very pregnant, has no husband or even current boyfriend, can't pay her rent, has hormones doing whack to her body and mind and has an active toddler from a man who is taking her to court, again, to get custody. Maybe rightfully so, but she was being pushed to the limit from many sources, internal and external. She didn't have the coping skills to handle her reality. Where are HER parents? Why wasn't she being taken care of better? Not everyone can do this, alone and broke. It breaks THEM instead.
Maybe not evil - just immature, exhausted and hopeless and took it out on the one who wouldn't let her get any sleep.