ANSWER:

If they are praying in congregation, this is totally prohibited. Women must stand behind men.

But if they are praying alone and they are mahram to one another, this is permissible. 

QUESTION: Can men and women stand side by side while offering the salah?

Prayer | September 18, 2022 1:17 am
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QUESTION: Is sitting on the same same spot after fardh prayer is limited to those who pray in masjid or women praying at home also get similar rewards?
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QUESTION: Can I pray tahajjud by staying up all night then pray Fajr prayer and then sleep?