How could she get away with this?

Ok had a friend who was 20 had a baby from one guy dated my baby daddy for 4 months then after they broke up she went for his 15 year old little brother. The girl was 20 and little brother was 15. All she got charged with was aggravated assault! Do you think this is right? The guy she had a baby with was also 15 turning 16 she was 19. If this was a guy he’d get labeled a sex offender. Am I right or wrong? This happened in the state of Arizona.