Lady Bonesy's story is uncertain. We first saw her in Bonesy's timeline before he became a Bonesy. When Human-Bonesy's Lover was killed by his fiancee, Lady Bonesy appeared to sip his soul. Bonesy sacrificed himself and Lady Bonesy turned him into a Bonesy and restored his former lover to life.
Lady Bonesy was later seen when the Storyteller was killed. She assisted Bonesy in turning Teller into a Bonesy.
During Witch-Con 2018 in Atlantis, Bonesy found himself in need of an immortal's soul to trade the Wizard for Estelle's life. He brought in Lady Bonesy, who was sacrificed against her will and killed to bring Estelle back.
WTF is She?
Lady Bonesy, like Bonesy, was a grim reaper of sorts, who sips the souls of the dead or dying with a sextant-like pipe. She was immortal.
Lady Bonesy was mercurial and transactional; she didn't care about her friends as much as about money, and while she was happy to trade one soul for another, she was unswayed by the emotions of the dying.
Lady Bonesy was never very close with the rest of the cast, even when she was part of their singing group. She held herself aloof.