It can also mean someone who considers themselves getting ready for a show, but is always fat.
Example 1. Random bodybuilder finds a piece of ass at a gym or on a forum, he can say I scored me a chicagogirl aka. Erin, no matter the girls name or location.
Example 2. A girl is fat , eating on her treadmill and says she is prepping for the next show. You can say, hey, look at that chicagogirl prep over there.