This is with reference to your Fatwa: 98886, where it was said that "it is better for women to pray in their houses than to attend congregational prayers at mosque". However, I have read that praying behind Imam till Witr, is equivalent to praying whole night. Then how do women get this benefit during Ramadan where Witr is read behind Imam after Taraweeh?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

No doubt that praying in congregation is better than praying alone and that doing the night prayer (Qiyam) with the Imam is better rewarded than doing it alone. Such a reward is mostly in the mosque. Sharia has determined that it is better for the woman to pray in her home than to pray in the mosque.
So, if the woman is looking for that which is better for her, she should pray in her home even if she misses the congregation in the mosque and with the Imam.
Allah knows best.