Prayer: A Woman Praying Level With or In Front of a Man
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 873
If a woman stands level with or in front of a man and they both start prayers together, then based on obligatory precaution, they must perform the prayer again. If one of them starts prayers before the other, then based on obligatory precaution, the prayer of the one who performed takbīrat al‑iḥrām second is invalid, and the prayer of the one who performed takbīrat al‑iḥrām first is valid, provided that what is mentioned in the next ruling is observed; if it is not observed, the prayer of the first person who performed takbīrat al‑iḥrām will also be invalid. However, if observing what is mentioned in the next ruling is not possible, then the person should continue with the prayer, and it will be valid.