In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Answering your question, the late Saudi scholar, Sheikh Ibn Baz (may Allah have mercy on him) stated:
If you made Witr during the first part of the night and then Allah made it easy for you to get up in the later part of the night, then pray whatever Allah has made easy for you in sets of two without performing another Witr. This is because the Prophet (peace be upon him) said,
“There are not to be two Witrs in one night.” (Ahmad, Abu Dawud, An-Nasa’i and At-Tirmidhi)
Furthermore, Aishah reported that the Prophet (peace be upon him) used to pray two rak`ahs after Witr, while he was sitting. The wisdom behind that, Allah knows best, is to show the people that it is permissible to pray after the Witr prayer.
Almighty Allah knows best.
Source: Islamic Fatawa Regarding Women, Compiled by Muhammad Ibn Abdul-Aziz Al-Musnad and translated by Jamal Al-Din Zarabozo, Darussalam, 1996.