Originally Posted by
pinetree
That's because her relationship to Daji hadn't really been made clear until recently. Also that is Tamamo's actual legend outside of Fate's characterization.
Foxtail just did a chapter exploring her past but you won't see any new info if you've played Extra. CCC is the sequel to Extra and even has a scene with Amaterasu herself.
It's mostly stuff that's been inferred throughout her appearances and other character's reactions to her. The recent Tunguska event in FGO has a bunch of info on Daji, but doesn't involve Tamamo.