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.
Scholars held it disliked for a woman to shave the hair of her head. This was stated by Imaam Ibn Qudaamah in Al-Mughni and Imaam Shihab Ad-Deen Ar-Ramli in Nihayat Al-Muhtaj. Ar-Ramli said:
Some scholars excluded from the reprehensibility of shaving the head of a woman the case where there is a disease in her head that might be eliminated only by shaving the head so as to treat pimples and so on.
Al-Buhooti who is a Hanbali scholar said in Kashshaf Al-Qina’:
It is disliked for a woman to shave or cut the hair of her head without excuse, because Al-Khallal narrated through his own chain of narrators on the authority of Qatadah that ‘Ikrimah said: "The Prophet, sallallaahu ‘alayhi wa sallam, prohibited that a woman shaves her head." If there is an excuse like ulcers, then it is not disliked. It is forbidden for a woman to shave her head as a manifestation of grief for an affliction like slapping the face or cutting the dress.
If there is no treatment for hair fall except by shaving, then there is nothing wrong in doing that.
Allaah Knows best.