No, she meant she actually typed the notes in on her cellphone's ringtone composer option. It was on Hey Hey Hey, right //hikari? (thanks for filling in the song, btw ^^)
You're probably right that she composes many songs via cellphone. Even though she may have piano playing experience, that doesn't mean she still plays (or even plays well). Seeing as she is very busy, the phone seems like the best way to carry around your song ideas.