- She sneaked on her best friend to the teacher.
- Honesty has always been his best friend.
- Did it ever occur to you to be betrayed by your best friend?
- I could not stand it in silence any more and disclosed it to my best friend.
- He is my best friend, my second self, as it were.
- He was surprised to discover that his best friend had turned traitor.
- You are my best friend.