[Omm AL-Homayra'a]

Translated from a fatwa for Sheikh Saleh Al-Fowzan [here]:

Sheikh Saleh Al-Fowzan (hafizahu Allah) said that the most important thing that she has to cover herself completely i.e keeps her piety.
He also added that she can wear whatever she wants, yet she shouldn't imitate what men usually wear.
Prophet Muhammad (Salla Allah 'aleyhi wa sallam) said: Allah cursed men who imitate women and cursed women who imitate men.