Yes, I am aware that the Queen of England is not Catholic; she is the head of the Church of England. She does not have the privilege to wear white when having an audience with the Pope. She has visited the Pope and wore black.

Camilla is also Anglican (or Church of England) is not a Queen and not Catholic and is not likely to become either. Yet Camilla did wear white to an audience with the Pope AND did not wear a hat or head-covering, thereby going against protocol.