Up to you

Dialog I

A: That was Sherry. She wants me to go to Hong Kong next month.
B: Why don't you?
A: I don't know whether I should go or not.
B: I think you should, but, it's up to you, of course. Do whatever you want.

Dialog II

A: Do you think I should make the donation?
B: It's up to you.
A: I really don't know what to do.
B: Don't ask me. I'm not your mother.