How about secondary protagonist and tertiary protagonist quaternary protagonist

She has to be the main protagonist of the Equestria Girls sub brand for these five reasons...

1. The four films showing her go from a school bully to a nice girl.

2. Being the only one in the current cast to hail from Equestria.

3. Being the leader of the main group.

4. Her meeting two individuals who underwent the same problems as her i.e. (Sci-Twi in My Little Pony Equestria Girls: Friendship Games and Starlight Glimmer in Mirror Magic).

5. The one who specializes in Equestrian Magic in the human world and the one who bought it there.

Whoever wrote the page about SCP-579 forgets to add 579 to category.