All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
As mentioned in many Ahadeeth, a woman – just like a man – can remain in the mosque provided that she should be free from menses and from Janaabah (state of major ritual impurity).
Also, as it is well-known, the fact that the Prophet's prevented menstruating women from staying in the mosque, it means that it is permissible for a non-menstruating woman to remain in a mosque.
Therefore, there is no objection to hold sessions of knowledge for women in a mosque although it is better to hold such sessions in other places so that menstruating women can also attend, and the benefit will be greater and more valuable.
Allah knows best.