One of my friends at school has turned toxic. How do I discuss it with her? | Ask Annalisa Barbieri

Ask a few gentle questions, and do it face to face. But it’s not your responsibility to fix things
• Every week Annalisa Barbieri addresses a problem sent in by a reader

I started high school last year with some friends I’ve known for a long time. One of those friends has started to act toxically with other people.

I have been distancing myself from her for a while, but nothing seems to work. She is really sensitive and has a history of dishonesty, which makes confronting her about my feelings incredibly difficult. She talks badly about many people, but pretends to them that they are the problem.