If females don't want to go into programming then don't make them.
There are really good female programmers, but males tend to be more frequent.
We all have different traits that make us good at different things, that's the beautiful thing about humans.
But if there is something to address, address the pain points specifically and directly.
Don't try to guess a "correct" ratio and work backwards with affirmative action (denying one race to boost up another).
For all you know the current ratio is the realistic ratio and where we should be.
In reality, the proportion of women in STEM directly matches the proportion of women in STEM majors, which directly matches proportion of women who say they're interested in STEM.