Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear sister in Islam, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
I`tikaf is recommended by the Sunnah for both men and women. The Prophet (peace and blessings be upon him) performed i`tikaf himself and so did his wives during his life and after his death.
Accordingly, there is nothing wrong if women perform i`tikaf in the mosque provided that this will not cause any negligence to the rights of their husbands or that of their children.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
It is permissible for women to do i`tikaf in the mosque — provided they have special arrangements for them to do so. Most of the mosques in the city [Toronto], however, do not have adequate facilities for women. Sadly enough, we find women often being relegated to a dark room or crowded corner, which is indeed a disgrace to womanhood. It is undoubtedly against the teachings of our beloved Prophet (peace and blessings be upon him), as he always ordered us to treat them with respect and dignity.
So until proper arrangements are made for women to observe the Sunnah of i`tikaf in the mosque, it is better that they do it in their own homes. For as scholars and jurists such as Imam Abu Hanifah have ruled, women may perform the Sunnah of i`tikaf in their own musalla (Prayer place) at home.
Women, however, need not despair; they may do well to recall an important point raised by Imam Shah Waliullah in his study of the philosophy of Shari`ah. He says that the Shari`ah is based on a fine principle of compensation which allows a person who cannot do a certain act of worship to reap the same rewards by doing what he/she can possibly do according to his/her circumstances or means. This is because of the fact that the Shari`ah is based on the infinite mercy of Allah, Who dispenses His graces freely to all of His servants.
Excerpted, with slight modifications, from: www.muslims.ca