>>5704261She's supposed to be Tamamo no mae. She wants to be a good waifu to help make for up for her past life full of manipulation and murder as an Imperial courtesan (high-class prostitute).
The historical accuracy part of F/E characters was just a novelty and not something they were striving to follow very closely. Emiya isn't a real historical figure and female Nero didn't burn/persecute people (victim of smear job) and was much nicer to the average folk than the real male one.
