Women wearing pants is not so simple.
At first, there was a problem with it because pants were a man’s garment. However, that changed many years ago. Pants are now regularly worn by women, and are even made specifically for women. I was told by more than one Rav that lo silbash does not apply to women wearing pants anymore.
The reason usually given now is that pants usually draw attention to the legs and other areas, and are therefore not tznius. However, that doesn’t apply to all pants. Some pants are more tznius than a lot of skirts that women wear.
As I said, it’s not a simple matter.