The size discrepancy has always bothered me, so I decided to measure them.
Harley Quinn, 7.25-inches = 1/9 scale = 5 ft, 5.25 inches tall "in real life"
(If we assume 1/10 scale, HQ would be 6-ft tall! Not happening in my book...)
Batgirl, 6.5-inches = 1/10 scale = 5 ft, 5 inches tall "in real life"
I really wish that DC would make these mini statues consistently scaled with each other. At least use the same scale
within a line, lol.