The Goq – I just want to point out that you don’t know BY girl’s friend, so it doesn’t seem like what you’re saying is LH, but since BY girl knows her, it is probably LH for you to say something negative about her to BY girl.
This is a common mistake and one that I probably make all the time. For example, a friend could be talking about someone w/o mentioning the name, and I’ll say, “That’s terrible, how could she do that?” w/o stopping to think that it’s LH since she knows who the person is even if I don’t.
I’m also not sure that you are right. I think what she meant is just that Chofetz Chaim has a very specific hashkafa and she wasn’t sure that it’s right for BY girl, but then it was hard for her to explain exactly what she meant because these things can be hard to explain (especially when you’re trying hard to avoid LH).