This is fanart for the Final Fantasy Tactics x Saga of Tanya the Evil fanfic called "Would that I were born no Princess", where Tanya gets reincarnated as Princess Ovelia where she unintentionally gets a more active role before the events of the War of the Lions. Also the Red Chocobo is Ovelia/Tanya's personal ride named Visha.

Link to the fanfic: https://forums.spacebattles.com/threads/would-that-i-were-born-no-princess-youjo-senki-final-fantasy-tactics-wotl.805228/

Its TVTropes: https://tvtropes.org/pmwiki/pmwiki.php/Fanfic/WouldThatIWereBornNoPrincess