She hasn’t been. It’s a fandom-made conclusion that’s taken as fact. While Madagascar is mentioned in a Volume 6 strip–and sometimes in Japanese characters are referred to in the third person–nothing has been confirmed and it’s not official, albeit alluded to.
All the official characters can be found on the English translation of Hima’s blog. I’d recommend checking it out! [x].
Ellawritesficssometimes 