The fact that I did "Let her wear Violet" relationship step immediately after signing the contract might matter.
Quests are not always available in any order. Therefore, the time of the quest, theoretically, may not have come yet. Story quests have a higher priority.
It happens I had already run out of story quests before I signed the demoness's contract.
...and anyway, the oracle shouldn't be saying "let her win" if relationship progress is being blocked by a story quest.
