I think it's fine. I know a whole family of boys who all go by their middle names (which are much weirder than their first names). For instance,
John Ocean goes by
Ocean,
David Willow goes by
Will, and the other boys (whose first names I can't remember) go by
Brahma and Coyote. As long as she introduces herself as
Ophelia (lovely combo, BTW), she'll be
Ophelia.