sorry.. Finding another manga again. Its shoujo

i saw this comic in a short in YT, it was a light pink haired FMC in a royalty setting. She has a brother(?) Who is black haired and what i really can remember accurately is the mentor(?) who turned into their family enemy. There is something in the pink haired fmc that ties her with the white long haired mentor. I forgot if the mentor has the power of a dragon or something but hes powerful and the last chapter was them fighting. And the fmc reasoning with the white haired mentor to stop whatever hes doing. The art is very good and especially the costumes!!! Very detailed. Is what i can remember.