I see this all the time, the victim is too blinded and lovestruck to even have the thought that they are even dating a tool. She will learn with experience.

Well, you can't force her to listen. She's going to do what she wants. You spoke your peace and now, it's up to her. It's not your fault that she allows herself to be screwed around with. All you can do is warn her and try to get her to see the reality of it all. After that, she has to learn on her own. She's not seeing what you're seeing and sometimes people just have to learn the hard way before they see the person for who they really are. If she has strong feelings for this guy, she's going to be naive about the situation. There's not a whole lot you can do, because she has to make decisions for herself.

Whether or not you stay friends with her is up to you. If it really bothers you that much, you don't have to bring it up with her anymore. You've talked to her about it and if she's not going to listen, let it be. If/when she sees this guy for who he really is, you can make the choice to be there for her or not. It's really up to you. You don't have to let this affect your whole friendship. You can't expect her to do what you want. She has to learn from the experience, so she won't put herself in the position to go through it again the future.

Hey there

Look dude, what do you think is the best way to learn? Like kids for example. Mom's all "stay away from the candle". That don't matter, you still play with it. Mom's all "I said DON'T touch the candle" Yeah like you'll listen. You burn your finger. "See? What did I tell you? Come here let me help you make it feel better". You don't go near the candle again.
That's all a metaphor obviously. The best way for people to learn is to go ahead and crash through it all thinking to hell with the consequences, and when they make mistakes - that's when they learn. When it comes around and bites them on the ass. After that you don't rub it in, you just be there for them.
Let this Brianna make her mistakes with this guy, and when something bad happens, you help her like a friend should. If you try to stop her, she won't learn for the future that guys like this are bad. But if you let her find out for herself, she won't make the mistake again, and she'll be a wiser person.

Trust me dude, let time deal with this aye?

Huggles from Anna