-used to make eye contact, or once eye contact is made used to let her know just what you are thinking.
-also if one says yeah girl to a woman and she responds with yeah girl herself, you must follow up with the words " i love you".
(hot girl crossing the streetin short shorts while jogging)
When the phrase is said, the 'yeah' is usually dragged out, while the girl is short, like this:
"Lady Gaga has no talent whatsoever."
"Yeah girl, I am so stoked for this weekend!"