Bevendre

It really depends on what you consider an OC.  In the case of Solar Flare, I would consider her a pseudo-OC for a few reasons, namely that the design is original and not taken from the show, and that the characterization is original, even if inspired by the show.  If you consider her Celestia still, then she is as you openly acknowledge that Solar Flare is a potential outcome for a well established character, but without that background she can and likely is considered an OC.

Papillon is much the same, but slightly different.  While I did base the design off of Fleur de Lis, the character had been featured so sparingly in the show, and with so little input or support that I had to put a lot more into her character.  If you look around, my version of Fleur is so vastly different from the generally accepted ideas that there are many who thought that she was my OC to begin with.  As for Papi, she was originally Fleur but she was my Fleur and not anyone else’s, and she has come to be much more than simply a changeling Fleur.

If you consider your Solar Flare to be an offshoot of canon Celestia instead of an OC, then continue to call her such, and defend it.  If you feel that Solar Flare has drifted so far from a canon representation to have broken from it, as I often feel with Papi, then taking offense at someone calling her an OC shouldn’t get to you.