I think you're right, it's the lower crossbar ("stepover") from the neck to the vertical seat support (or lack thereof) that signifies a girls bike. They were designed that way back in the 1800s when women wore dresses, so it wouldn't show too much leg when they hopped on.

Mine had blue flecked metallic paint - damn I loved that bike! I can still remember seeing it for the first time on my birthday - thanks again dad!