Amina Inloes, Amina Inloes is originally from the US and has a PhD in Islamic Studies from the University of Exeter on Shi'a hadith. She is the program leader for the MA Islamic Studies program at the... Answered 1 year ago

There is some discussion of this topic here:

The main reason why it is unlikely that a woman will become a marja' today is not theoretical, since there may be many approaches to Islamic law, but rather is practical. That is, there are social forces that would push a woman off of the path of becoming a marja', and women do not have the same networking, educational, or social  support that men have and which people need to succeed in any field. (Although some Iranian women become mujtahids and there are structures in place in Iran to facilitate that, less so in other countries although it occurs in other countries also.) Furthermore, women who are religiously conservative are generally encouraged to avoid positions of public leadership or to avoid being publicly visible.

Maybe in the future it will be different.

However, it is worth considering that there are many forms of religious and spiritual leadership. While we focus mostly on the role of the marja' as the chief jurist, or chief legal expert, people require guidance and leadership in many areas of life, including family matters, spiritual guidance, ethics, politics, charitable work, and so forth. Some marja's do offer guidance in these areas also but not all do, as it is not possible for one person to specialize in every single thing or to do every single thing at one time. Furthermore, even within the Islamic sciences, there are other areas of expertise that are also important such as tafsir. So it is also valuable to become a leader or expert in other areas of religion, not only jurisprudence/law.