After creating a new girl, I wanted to save it. when I pressed Save, the game freezes.

Not sure why you have this problem, Maybe mods?

Try running the game as Administrator, Maybe that will fix it.

If you have mods installed then:
Try reinstalling the mods that you installed after you got this problem.

As a last resort you can always reinstall your game! But try what I wrote above first.

This happens to me if I change the window size after starting the game. If I want to save I just make sure to set the resolution I want and not minimize/maximize during runtime.