My best friend tells her boyfriend EVERYTHING?

Ok, my best friend has been in a relationship with her first boyfriend for 1 1/2 months. Everything is fine, except everything I say to her, she goes and tells her boyfriend. It hasn't really been that big of a problem unless its a serious conversation. Like for example, i was talking to her boyfriend on the Facebook IM (he is also my other best friend), and he started implying that he wants to have with her before their married (we are all christians and have christian beliefs so don't go saying it is okay to have y before marriage, thats not the point of this question). It started bothering me so I finally told my best friend. I even remember making her swear not to tell her boyfriend or anyone else that i talked to her about that. Yet, ten minutes later, her boyfriend calls me, freaking out on me, for "implying that he is using her" and "him trying to convince her for fifteen minutes that is not why he goes out with her". Now, he is mad, I'm mad, and my best friend is a blabber mouth. What do I do? We used to be inseperable now I can't tell her anything?