AhsanAllahu ilaykum There was 8min left for maghrib but me & mother finished the salah on time. However she falsely thought the final tashahhud was the first and only said tahiyat, nothing else. Once i as imam gave salam, she did too-was her salah valid? She also repeated her salah but time was over

Ustadh AbdulAziz al-Haqqan

No need to repeat.