Girlfriend wants to live with other guys - What can I say to her now?

So last night my girlfriend who is almost 18 tells me she has plans to move out and live with her guy friends instead of living with me in the near future. Should I be offended or what cause I feel so hurt because back in August we talked about living together after she graduates high school and stuff but now I just feel so hurt and betrayed and breaking up with her keeps playing through my head. Please give me some advice, thank you every one. Oh and just to add her reasoning for not wanting to live with each other is she thinks it might break us up because of some like statistic with couples that live together, which I agree with but going to live with other guys is NOT going to make it better for me. (The guys by the way have been her friends for like 4 something years, she has had with one of them one time and given head to both of them at one point or another which is what gets to me so bad) Any advice on what I should tell her the next time I can sit her down would be greatly appreciated!