What is the ruling on a female transforming herself into a male, and is it permissible for her to perform Hajj and Umrah without a mahram after her transformation, and is it permissible for her to marry?

One must differentiate between "gender correction" and "gender reassignment."

Firstly: Gender correction is performed on individuals who have a disorder in their gonads (hermaphrodites), where their sexual organs are ambiguous. Its purpose is to affirm the true gender of the person, whether male or female. This type of operation is permissible in Islamic law, and it has been ruled permissible by scholarly bodies, because it is considered a treatment for an illness and not an alteration of God's creation.

Secondly: Gender reassignment involves changing a male to a female or vice versa for a normal person with complete organs, and there is no medical justification other than the desire for change. This type is forbidden in Islamic law and is considered tampering with God's creation, as stated in the Almighty's قوله تعالى: (وَلَآمُرَنَّهُمْ فَلَيُغَيِّرُنَّ خَلْقَ اللَّهِ) "and I will surely command them, and they will alter the creation of Allah."

If the operation your friend underwent was of the first type (gender correction), it is permissible, and the rulings of the gender she transitioned to apply to her. However, if it was of the second type (gender reassignment), it is forbidden, and it does not entail a change in Islamic legal rulings; she remains of her original gender.