You get the code language your friend uses on the phone. Should you tell her so?

You are a young college student sharing a room with your friend...

You are a young college student sharing a room with your friend. Sometimes, when your roommate is on the phone and does not want you to know what she is saying, she speaks in a kind of code, inserting extra syllables into words. She thinks you do not understand when she talks about you, but you do. Is it your ethical obligation to tell her so?