All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We advise the parents of this girl to fear Allaah, the Exalted, and His punishment. It is impermissible for the parents to command their daughter to wear trousers before non-Mahram male relatives such as her maternal or paternal cousins or attend public parties wearing clothes that do not conform to the Islamic code of dress. This is impermissible and it is an evildoing that no Muslim could approve of. The daughter should not obey her parents in this regard since she is obliged to obey them only in what pleases Allaah, the Exalted.
As for you, you should adhere to patience and hope for the reward of Allaah, the Exalted. You should not obey your parents in this regard and should also strive in convincing them by means of a useful book or an impressive audio tape or by connecting them with pious and righteous people. You should talk wisely and leniently to your parents about that.
Allaah Knows best.