Not just MAJOR CHARACTERS, but also SUPPORTING CHARACTERS need to make progress or change in a good story. It takes only three or four beats to establish transformation:
(1) establish the character as selfish;
(2) illustrate further selfishness, this time with someone reacting to it;
(3) do it again, with her registering the reaction; and
(4) show her doing something, even something small, that is unselfish.
With strokes like that, you’ll be considered a master of character-building. It’s that simple.