Years ago, I read a mystery about a college student named Shannon getting a summer job at an old house run by two old ladies (sisters). Students dress as Gibson girls & do tours through the historic house. Shannon befriends another girl student. There’s a guy that took a summer job there too. He’s a writer, I think his name is Michael. A relative of the Sisters also lives there. She likes caramels. There’s a murder. I think the Sisters names are Cora & Lanie or maybe Lennie.