I read this book in the 1980s. I remember for sure that the girl’s name was Drucilla, spelled with a “c” not an “s.” I think she had long black hair and was tall and thin, and she was possibly magical, like a young witch. I think she was an outcast; maybe the story was about her finding a friend? Definitely NOT from The Worst Witch series. I remember it being kind of moody, with Edward Gorey-style ink illustrations.
There’s a book called All the Way to Wit’s End about a girl named Drucilla. She isn’t magical, but she lives in a home filled with antiques and she wants to fit in when they move to the suburbs, so she tries to sell them off.
I don’t think this is it, but thank you!