I'm not a Harry Potter or Downton Abbey fan, but I see she was also Mother Superior in Sister Act, Granny Wendy in Hook and Thetis in Clash of the Titans (the original one). I remember her well in all three roles.
89 is a good long life to live and she spent most of it as an actress, which is, I assume, how she wanted to spend her life. Her last film was The Miracle Club, which came out last year, and she has a film called A German Life which is still in production, so it sounds like she got to do what she wanted to the end.