Women pants

Devarim (22:05) The woman shall not wear that which belongs to a man, neither shall a man put on a woman’s garment; for all who do so are abomination to the Lord your God.

Rambam (Avoda Zara 12:10) A woman should not adorn herself as a man does - e.g., she may not place a turban or a hat on her head or wear armor or the like. She may not cut the hair of her head as men do.A man should not adorn himself as a woman does - e.g., he should not wear colored garments or golden bracelets in a place where such garments and such bracelets are worn only by women. Everything follows local custom. A man who adorns himself as a woman does, and a woman who adorns herself as a man does, are liable for lashes. When a man removes white hairs from among the dark hairs of his head or beard, he should be lashed as soon as he removes a single hair, because he has beautified himself as a woman does. Similarly, if he dyes his hair dark, he is given lashes after dyeing a single hair.

Minchas Yitzchok (II #108) It is absolutely prohibited for women to wear modern pants even if they are the colors that men would not wear. Since these are disgusting garments and are designed to cause sin. Inj addition they are prohibited as male attire even if they are altered to be different then the pants males wear. . 

Rav Ovadia Yosef (VI YD #14.7) Question: Is it better for girls who insist on wearing very short skirts to be encouraged to wear pants instead? Answer I agree that women and girls should not be totally permitted to wear pants because they are licentious garments and they draw more attention to be looked at than the dresses or skirts they normally wear and thus cause lustful thoughts. Proper Jewish women  should not wear them at all especially the tight ones. Nevertheless for those who insist on wearing very short skirts  despite the protest of parents and teachers it is best to pick the lesser evil and ask them to wear pants instead. 

Rav Ovadia Yosef (VI YD #14.8) Question: Is it better for girls to wear pants instead of short skirts?Answer:It is absolutely prohibited to wear short garments even if they also wear transparent stockings. It is especially a problem for students siting in very short garments before a male teacher who is teaching them about holiness.  The thousands of young men who died in the recent Yom Kippur War, perhaps they died because of the sin of immodesty of the women. In addition following fashion trends and wearing mini dresses is a violation of the prohibition of not being like the goyim. Thus it is obligatory to chastise those who wear short garments especially the students in the religious schools and encourage them to be modest

Rav Ovadia Yosef (VI YD #14.8) Question: Is it better for girls to wear pants instead of short skirts?Answer: In conclusion regarding the actual halacha. It is absolutely prohibited for women and girls to wear short dresses or skirts which are called mini.  There is also the Torah prohibition  not to be like the goyim and therefore they should not be given permission to wear them since they are despicable  and immodest  It is best to try and reason with them to only wear modest clothing that covers the knee when they are seated. However if they won’t listen to reason to dress modestly. It is better that they wear pants than mini dresses and skirts until they can be influenced to wear modest clothing.