I've never heard "posenger' aloud but in my head at least, my god what an ugly word.
PAUS-EN-JER?
POSE-N-JER?
Ugh. If she had a legitimate claim to messenger culture than I could almost, dimly, see a reason for her argument, but sucks to her if she's wearing a messenger bag without biking (let alone actually messenger...ing) and wants to argue merit/authenticity.