Help.. What should i do?

Ok my friend is dating my this guy... Shes my age n im 14.. N they have done alot for their age!! I worry about her cuz he treats her wrong!! Like he made a very nasty prank call n it scared us soooo bad... But i worry about her cuz she has done things that you shuld wait n do wen ur married!! I jus dont know if i shuld step in n say Sandy u dont need to let him b a jerk to you n let him walk all over u like that!! U shildnt take crap like that! Jus tell me what i shuld do! Please!!! Thanks :)