Ikrimah (may Allah have mercy on him) narrates from Ibn Abbas (may Allah be pleased with them both) that when a woman leads women in prayer, she should stand in the middle of them.
We have narrated a musnad (connected) hadith on this in the chapter on the call to prayer, and there is weakness in it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5358