Stargirl is full of important events. I think one of the events should be Stargirl's coming to school for the very first time. She is an outsider in so many ways, but the school eventually embraces her to the point that she is on the cheerleading squad.

I would include in your list the time that Leo goes to Archie's house to ask about Stargirl. Leo just can't figure out if she is the real deal, and Archie confirms that she is.

The list should include the disaster that Stargirl's appearance on the Hot Seat show turned into. I believe any list should also include the time that Hillari Kimble slaps Stargirl, and Stargirl's response is to kiss Hillari.

One more important event would be when Stargirl decides to change herself and act "normal" in order to please Leo. Her transformation is not a good thing, and she begins to feel depressed quite often.