Wa Alaikum Assalaam,
The general law is that the pilgrim must remain at Muzdalifa to perform Fajr Salah and then do the wuqoof after this. This is essential (wajib) and if one does not do this, one will have to pay a dumm (penalty). The penalty is that of sacrificing a sheep or a goat at Mina.
Normally, it will be sufficient for one to give someone the money for this animal, who will look into getting the animal and sacrificing it. However, with respect to women, old, weak and sick people, this ruling has been relaxed. The Prophet (S.A.S) has allowed such people to leave Muzdalifa before Fajr Salah, at the last part of the night, so that they may not be harmed on account of the massive crowd that leaves Muzdalifa to go to throw the pebbles at the Jamaraat. Such people are allowed to leave Muzdalifa without doing the wuqoof and there will be no penalty upon them.
Therefore, as a woman if you leave Muzdalifa before performing the Fajr Salah and did not do the wuqoof, there will be no dumm (penalty) on you.
And Allah Knows Best.
Mufti Waseem Khan.