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 questioner, we are really pleased to receive your question and we pray to Almighty Allah to help us furnish you with a satisfying answer.
As for the question you posed, the majority of Muslim scholars hold the opinion that a woman can lead other women in congregational prayer.
Here, we would like to cite for you the fatwa issued by Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee:
'It is well known that congregational prayer (Salatul-Jama`ah) far exceeds individual prayer in reward, and there are many hadiths that support this. It is reported that the Prophet (peace and blessings be upon him) said: "The congregational prayer exceeds that of individual prayer (Salatul-Fard) by twenty five or twenty seven degrees."
A woman is allowed to join the congregational prayer at mosques. The same rule applies to a woman who wants to join a congregational prayer in her house along with her family, as well as at her work or even at school where she studies or teaches.
Imam Malik states that a woman, under any circumstances, is not allowed to lead other women in congregational prayer.
The majority of jurists, however, maintain that a woman is allowed to lead her fellow sisters in congregational prayer if there is no man to lead the congregation. They cite an occasion to support their view. The Prophet (peace and blessings be upon him) is reported to have appointed a muezzin to Umm Waraqah (may Allah be pleased with her) and allowed her to lead other women in her household. Also, it is reported that `A'ishah (may Allah be pleased with her) used to lead women in congregational prayer and she would stand along with them in the row. So did Umm Salamah (may Allah be pleased with her).
Some jurists maintain that when a woman leads other women in congregational prayer, she should stand with them in the same row and she is not allowed to stand in front of them.
Others say that even if the woman leads other women in congregational prayer, then her prayer as long as the prayer of women praying behind her is valid as there is no clear evidence which states otherwise.'
Allah Almighty knows best.