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.
It is sufficient and acceptable for a praying person to sit in any manner during Tashahhud, but the Sunnah is to sit upon the left foot and keep his right foot upright except in the prayer which has two Tashahhuds (i.e. the prayer of three or four Raka'hs), then it is recommended in the last Tashahhud to spread the left foot out under the right leg and sit on his buttocks.
Women are like men in this regard for the general meaning of the religious evidence and for the Prophetic narration in which the Prophet said: "Women are the twins of men.” [Abu Daawood]
However, if a person is unable to sit according to the recommended way during Tashahhud, then one may sit with crossed legs or in any other position, but it is disliked for one to sit on his buttocks and cross his legs.
Allaah Knows best.