How can I save her from what's to come?

If I was her, I think I would just want to hear the truth, that its coming from a good place when you tell me this and you don't want to see me get hurt, that's why you are sharing this, and for those reasons you don't think he is ideal for me. Given more or less

my brother use to warn all the chicks, all you can do is leave a secret letter saying, you don't know me but ill like to let you know " this guy blah blah" is trying to hook up with you to just have sex, this letter is not to scare you, but just a person who hates to see guys use girls like this.
im sure she will appreciate it

You can't save her. And warning her could make you seem like the petty jealous type. Just let her find out on her own and be there to pick up the pieces.

I definitely agree with the others and make yourself the one she wants to talk to. Talk to her, show her how much better you are than that other douche bag.

You're in a difficult position also because if you tell her that he is no good then she might just think you are jealous and not believe you and she wil find out the hard way.. but I think it is better that you warn her, politely, that he isn't a decent guy.

Inevitably it is her problem, but if she is a smart girl she will at least listen to your warning and keep it in mind and hopefully figure it out for herself before she does anything stupid.

Step your game up and get her for yourself.talk to her, be charming and appealing and go after her

All you can do is tell her that you don't think he is a good guy for her. That's it.

People have free will.

Does she know you know him? Because if she doesn't you can just say off-hand to her how you heard about this crazy guy who does all this bad stuff and when she asks who it is, tell her. If she does know you know him, the only thing you can really do is out charm him. I know that's hard to do when you're shy, but you have to try. The best defense is a good offense.

Just tell her that he sucked a dudes d***. And also, not all potheads suck d***. I just want that to be known.

you have to man up nad also make a choice make her want you and tell her how you feel and go out and then tell her about the guy a little later on so she don't think you just said that to get her won over or prob never tell her and tell her about the guy right away and have her most liky not take your word pick your choice coff coff choice 1