Maggie Q is a stage name, her real name being Margaret Quigley.
Many countries and states have Surname laws and Naming laws: see Naming in the United States. It depends on local legislation, cultural laissez-faire, and practicality for data entry. (If you make your surname a single EMOJI, I am coming to get you!) But in places like Kentucky, that have no naming laws on the books, the answer is yes.