'Rosie' is a name given to an attractive girl who just can't seem to have many relationships with guys. The boys wanna bang her, not date her. She'll listen any time, and take on your problems as her own. She has a certain mystical appeal and sometimes things just happen which she can't explain. She HATES it when you call her Rosy with a 'y'.
Rosie: "I can never seem to get a boyfriend!"
Friend: "I guess they'll bang you, just not date you"
Rosie: "Fat load of help for me then."