This strip hopefully explains that Luna has been in a Time Loop. What I mean by that is that Luna first became a super hero, then the super hero went back in time and altered things, causing her young self to grow up to be a villain instead. That villain went back in time and tried to stop Luna from heading down the wrong path, but it didn’t work and she became a villain anyway. 
Now THAT villain version of Luna has come back in time for the same purpose, but this one has decided to just go with it instead of trying to talk little Luna out of becoming a villain.
I know the theory that if you have to explain it, it’s not very good.  To that I say….
“uh… oops…”
John Vogel