Angels have free will, mankind has free will, people never seem to remember that Jesus had free will too.
I feel sometimes that sometimes this discussion seems to sell our Lord short. It is as if Christ had no choice in the matter. Mary had a choice, she was not told that she had to do something. “Let be done according to thy will.”
Christ, our Lord and savior was also a man. “Father, if you are willing, take this cup from me; yet not my will, but yours be done.” Luke: 22:42
They did not do this for any personal reward, yet rewarded they were. Christ our savior shares in the Trinity that is Kingship of the Universe, Mary, is Queen of Angels, Saints, and the Universe, both still working actively to save mankind all of mankind from Satan and themselves.