When a woman leaves her home and is in the presence of non-mahram men, she is obliged to cover her skin by not wearing anything see-through and by that which does not reveal the shape of her limbs, which rules out tight jeans and tops etc.
During prayer, on the other hand, if she was to pray with tight clothes that show the shape of her limbs, but do not reveal the colour of her skin, then her prayer is valid, although it is disliked for her to do so.
So, pay attention to the difference between these two things.
— Taken from Sh. Muhammad Abdu-l Wahid al-Azhari (h)