Is it obligatory to inform a sister who led the prayer that she must re-perform the prayer in which she forgot a verse from Al-Fatiha, and should she inform those who prayed with her to re-perform the prayer?

Al-Fatiha is a pillar of prayer; prayer is invalidated by omitting any part of it, unlike the Hanafis who believe that omitting Al-Fatiha entirely or in part does not invalidate the prayer, but rather necessitates a prostration of forgetfulness (sujud as-sahw) if done out of forgetfulness, and is sinful if done intentionally. The opinion of the Hanafis is weak (marjooh), but acting upon a weak opinion after the fact is permissible. Therefore, the prayers of the women who omitted part of Al-Fatiha are valid, and they do not need to repeat them.