Question

what rights and responsibilities do i have when you are a friend of the person whose friendship was ended by their friend

Answer 1

The Golden Rule works.

Answer 2

what is the golden rule?

Answer 3

Act toward other people the way you want them to act toward you.

Treat others as you want to be treated.

Answer 4

Do unto others as you would have them do unto you.

In other words, treat other people the way you want to be treated.