All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
A woman's 'Awrah (parts of the body that must be covered in Islam) in front of other women is to cover what is between the navel and the knee.
Therefore, a woman must cover her 'Awrah with a dress that is neither transparent and exposes her skin nor tight and forms the size and shape of her body. In other words, wearing tight trousers would form her bodily parts, and thus, wearing them is prohibited.
For more benefit on the ‘Awrah (body parts that should be concealed as per the sharee'ah) of a woman in front of another Muslim woman and in front of a non-Muslim woman, please refer to Fatawa 92295 and 82459.
Allah knows best.