Does anyone have examples of mainstream-ish media that features a female character who sacrifices her life to save others in some big moment of heroism?
Not very mainstream, but in Mark Helprin's novel, Freddy and Fredericka, that female forest ranger forcefully substitutes herself for Freddy so that she dies in the fire, not him.
The show, "The Originals" ***SPOILERS***
https://youtu.be/PTmRA9MZMl0
It's a huge moment when you're watching the show because the character that dies was literally one of the main characters for a long time. Unexpected death honestly