This could go two ways:
It could be a power struggle - what's expected from her versus what's expected from you, and who "wins".
It could simply be a matter of character. You are responsible only for your own actions, no one else's. What they do is not up to you, and should have no bearing on who you are and thus what you do. If you go to dinner with someone, and you like them, you might like to treat them.