How can i talk to my best friend about how her seeing new bf is hurting me because

[bevcakes]

he is a douchebag? My best friend of 5 years recently started seeing my bf's older brother. He is a total jerk. He has told her that he hates me and his brother deserves better, and rudely told one of our other close friend that he has no chance of being with her because he is with her and he isnt good enough to be with her because he already bagged her. My bf, his little brother, even admits that he is a huge jerk and doesnt deserve a great girl like her. This guy is a huge selfish person and she just doesn't see it. I at first supported her because she is my best friend and if she is passionate about something i want to support that. But it has been going too far lately. NONE of our friends think they are good together and she has even admitted that he needs to change. But everyone knows he wont. I have even mentioned that she seems to pick the same kinda guy, and in her words "you mean one's that arent going anywhere?" she obviously knows its not good for her but it baffles me that she does it anyways. Another one of our friends mentioned to her that its not worth losing both of her best friends, (me and this other guy), because of this sleeze ball. He never wants to do the things that she likes to do, especially with her friends. But when he wants to do something she is always right there with him. I dont want to be one of those friends who gives ultimatums like choose him or me, but its to the point that its what all our friends talk about when she is not there, and I'm already considering not being her friend anymore because she is making ridiculous man choices. How can i tell her how serious this really is without hurting her and letting her make the right choice, instead of me forcing her to. It hurts me so bad to see her fall so hard, but she is an adult (22yrs) i just want the best for her..... thanks in advance