I know the other girls are your friends. I have difficulty staying friends with people whose behaviour I dont respect. If they can't suck it up, be an adult and get on with life, then I wouldnt have a lot of time with them. I certainly wouldnt buy into the whole, how do we tell her we dont like her stuff. My response would be, "this is my advice, if you dont like my advice, dont ask me again and don't use me as an excuse".

However, I am black and white about my values, my friends and relationships in general. I am also generally anti-social, and would eventually find catching a train with the same people regularly a bit smothering, so wouldn't be in that situation anyway.

Sorry, that doesn't actually help you at all, unless you decide to just back off and tell them you're not interested in talking about Betty. If they sort it out, fine. If they dont, that's their problem. Dont make it yours.