Help im in serious need!! idk what to do!!?

right my best female freind, likes an 18 year old... were both 14, she recently turned 14 about 2 weeks ago. this 18 year old keeps telling her lies, like "i love you!" and "your the most beautiful girl ive ever seen!!" and other shet like that. they met smokin weed. and now.. she sorta falling for him. she promised me and every one she wont date/do anything with him. i trust her. im just scared... idk what to do. she wont listen to me.. or anything.. i dont want to see her get hurt or lied to any longer.. help!!!