…to sacrifice herself.

Late 80s early 90s, maybe on disney, short film possibly, seemed like anime, in color, resembled radiohead kid a album cover style of artwork .  girl sets out on quest to save (something), has a small group of creatures with her to help. she needs to find a rose but a witch or someone is aware of this so the girl has to try to keep it a secret. possibly sees the last rose die (in a briar patch?) resulting her ending up in a castle and has to cut her horn off/die.