Lawyers! Need some help for a friend.

An old girlfriend of mine has been left with a $5,000 cell phone bill from her now ex-boyfriend. She stupidly put the family plan under her name and he used his phone to call his home country in Africa. He ran up a $5,000 bill and just yesterday broke up with her.

Will she be able to sue him or fight for her money back? Or is she stuck with that bill?