Umm Ayman (ra) was the servant of Rasulullah (saw) as stated by al-Dhahabi in his Siyar A'lam al-Nubala, Vol. 2, pg. 223. She had a status so lofty and high, the Prophet (saw) used to say she’s a woman of paradise.
So that proves she can't be a lair nazubillah
So that means the testimony she gives for fadak is true and abu bakar was on batil..
Alkarbala