you know a work has enough good female characters

when the fics have stats like this:

F/M (4782)
Gen (3796)
M/M (1506)
F/F (899)

That's A:tLA fics on AO3, excluding fics also categorized as Korra.

For comparison Star Trek is

M/M (35089)
F/M (17365)
Gen (15774)
F/F (4157)

Harry Potter is

M/M (118917)
F/M (78012)
Gen (48653)
F/F (15103)