Just tell her that she might want to sit down so that you can tell her that she's turning into one of those girls that you thought when you were in middle that was predicted to become pregnant before they turned sixteen.. what I'm saying is just tell her straight up..
Talk her with a low tune of voice and don't ever try to tell her in a bossy way. Tell her that you're only saying this because you care for her and you love her. :D Good Luck. :D
I would advice not to, because some friends are so impossible to understand someone, if you try to tell her, well, do it accurately because she might take it negatively :p
Just tell her straight up but she might think that youre being rude but when you really just trying to help her out by telling her. Beacause if u dont you might turn out to be the bad guy