Answered by Shaykh Amjad Rasheed
Is it permissible for a woman to stand next to her mahram (unmarriageable men) during the prayer?
Answer:
Yes, it is permissible for them to do that, but there is offensiveness in it. In our school, neither the woman’s nor the man’s prayer would be invalidated thereby.
الجواب : نعم يجوز ذلك لكن مع الكراهة ، ولا تبطل صلاةُ الرجل ولا المرأة بذلك عندنا