LOL! In Brosnan's films she was the new M meeting Bond for the first time. In Craig's she was M before Bond was even 007! Plus umm spoilers from the new movie.... That is a total reboot. Other franchises have rebooted totally and had actors returning to the same parts. But with no continuity to their previous appearances.
There is a very long list of this happening, in fact a few years ago I even created a thread about.