Here is a good reference book on all the evidence that girls' education is the world's best investment: https://gdc.unicef.org/media/3166/download
On the one hand, I believe that empowering women is incredibly effective for reducing war, keeping the population managable and protecting democracy. Moreover, the education will help thos girls grow up to become better mothers. I think that producing more engineers will be crucial for the future progress of technology and there are currently many women in developing countires that have no opportunity at all to become an engineer.
On the other hand, the global health and development fund has determined based on quantifiable results, that interventions in health are the most effective. This sounds terrible to say, but if we help people in poverty survive without solving their poverty won't that increase the number of people living in poverty?
To be clear, I'm aware that most experts no longer believe global overpopulation will be an issue, and I think more population growth could be good for the progress of technology.
I think the answer depends on your values. Personally, I do not assign intrinsic value to education. In a nutshell, my goal is to get to the star trek vision of the future eventually so I'm wondering what maximizes the chance of that or accelerates us getting there. In the past I've donated to help bolivia which does a combination of nutrition and education for boys and girls