I'm confused, the fake Starfire was Blackfire and the "real" Starfire was Jinx, no?

yup

yup

part 2

I wish but was that quite random. I have no clue how to continue this

It might be something like Jinx would like to be on a team where she would be respected and liked, which is why she dressed up as Starfire. After a moment's thought, Robin and Blackfire give her the Raven skinsuit, which is currently on a mission/trip with Starfire. And Blackfire would like to feel what her sister feels while on the team, so she decided to replace her. So Blackfire remains as Starfire until their return.

well duno. Not my style

Cute and good story!

thanks