This expression began as a reference to either the external female genitalia (labia majora) or buttocks. Using "Georgia Peach" is literally calling a woman "pussy".
The mainstream meaning of "cute girl" is often blended with the underlying meaning of "pussy" to create a double entendre.
"That is one juicy Georgia Peach."
The Allman Brothers album "Eat A Peach" album title played with this double entendre.
or they could just be talking about her back side if ya know what i mean
bob: yeah she sure does look good
Tommy: dang look at that fine Georgia peach
Tommy: right there can't miss her!
bob: she a ten for sure