In the Name of Allah, the Most Gracious, the Most Merciful.
As-Salāmu ‘Alaykum Wa-Rahmatullāhi Wa-Barakātuh.
If the rooms are not within the boundaries of the masjid, then a menstruating woman may attend the event there. However, if those rooms form part of the masjid itself, then it will not be permissible.[1]
And Allah Ta’ala Knows Best.
Abdour-Rahmaan Lim Voon Heek
Student Darul Iftaa
Port-louis, Mauritius
Checked and Approved by,
Mufti Muhammad Zakariyya Desai.
https://iftaa.co.za/9142/ruling-on-menstruating-women-in-rooms-attached-to-a-masjid/