Hannah Montana is the alter ego of which teen pop star?

In the television series Hannah Montana's alter ego was Miley Stewart, but in real life she is Miley Cyrus. Wiki says :Miley Ray Stewart is the central character of the Hannah Montana media franchise, portrayed by Miley Cyrus. The character was originated in the Disney Channel series Hannah Montana and also appeared in the feature film Hannah Montana: The Movie.

The answer would be Miley Stewart, those are the two names of the character in the TV show. The actual character, Miley Stewart, and her secret alter ego, Hannah Montana. Miley Cyrus plays the characters, but doesn't go around town pretending to be Hannah Montana.

If what your question really is is "What is the name of the actress who portrays Hannah Montana?" then the answer is Miley Cyrus. Miley Cyrus is a real person, Miley Stewart is a Disney character, and Hannah Montana is her alter ego within the show.

In the show, the alter ego is Miley Stewart because that is character's name. Miley S, is played by Miley Cyrus. In real life, Miley Cyrus doesn't have an alter ego. Technically, your friend is right.

Well Hannah Montana was the pop star by night and Miley by day in the show Hannah Montana on Disney channel. They were played by Miley Cyrus

Miley Cyrus?

Really! Miley Cyrus!