Horror-scopes: Is The Exorcist's Regan a true Scorpio?

Believe it or not, setting yourself the task of analysing fictional characters' birth charts is not as easy as say, training for a marathon, or learning Russian - least of all as these 'people'/undead murderers/demonic entities aren't real and haven't set up a cruddy cheap clothing brand on Instagram which means I can easily discover their D.O.B by looking them up on Companies House (journo trick of the trade there).
However, some films have a birthday party or birth at the heart of the story, The Exorcist being one.
Recently, my friend Sarah and I went to watch th