Actually you do have to get a model release on her. Touchstone, MGM, and Disney all get model releases on you and they are not doing porn.
If you are not using the picture to promote something (i.e. commercial use - advertisement, service, etc.) you can 'publish' a picture taken in a public place without permission. other than that I am almost sure you do need one.
I think we need jrv on this. jrv, if you don't mind?