Traits:
Crafty. Subtly intimidating/threatening. Watchful and observant. Protective. Judgemental. Stubborn. Lonely, gets excited about having company (esp. if she likes them) Produces a menacing aura upon revealing her vampiric nature.
In Japanese, she tends to use feminine informal speech among young people, women her age, frequenters of the library, or people she trusts. However, when she wishes to be assertive, she says "suruna" rather than "shinaide". Likewise there are signs in the library that use the masculine informal command rather than the respectful gender-neutral one. She also switches between using very old pronouns for herself such as "wachiki" or "warawa".
backstory:
She was likely an oiran, having lived a mostly privileged life if you excuse the lack of freedoms/options as a woman. One day, she was turned and decided to raise hell with her newfound power. I'm talking mass havoc here. Fires. Murder. Screaming. Really put old Japan through the ringer. Then she got bored and migrated to the Other World at some point. The library has been kind of her thing for the past so many years.
Kanji ideas:
Edith: They'd literally be BFFs. They would hit it off so nicely.