The one who still wore the wedding dress though the groom failed to show up for the wedding?
Yep. You nailed it. Wikipedia's description of Miss Havisham matches Hillary perfectly.
from the Wikipedia: Miss Havisham,
Miss Havisham is a character in the Charles Dickens novel Great Expectations (1861). She is a wealthy spinster, once jilted at the altar, who insists on wearing her wedding dress for the rest of her life. She lives in a ruined mansion with her adopted daughter, Estella. Dickens describes her as looking like "the witch of the place".
The "the witch of the place", yep, that's Hillary.
Miss Havisham also kept a rotting wedding cake in her drawing room and told Pip, “It’s a great cake. A bride cake. Mine.”
She was a tragic figure, a bride jilted at the altar.
Hillabitch is pure evil, balked of her chance to do more evil.