Wouldn't Lavinia Whateley have been more appropriate?
Lavinia isn't a Servant, and lacks the ability to freely traverse dimensions/worlds the way Abigail can. If anyone could stumble into Yharnam and interact with the Great Ones through happenstance, it's Abby. She is both the Gate and the Silver Key, along with having a direct link to Yog-Sothoth as a miko.
