Akuyaku Reijou no Tsuihougo! Kyoukai Kaikaku Gohan de Yuuyuu Sister-gurashi

Reincarnated as the villainess, Elizabeth Fontini fought against her fate, but it was all for naught. Repeated misunderstandings compounded with unfortunate circumstances lead to her inevitable downfall, and Elizabeth is banished to the nunnery. However, what most thought to be punishment is actually Elizabeth's long-awaited freedom! Life as a sister isn't too bad, but her short respite is muddled by the arrival of Leonid Guardhelm, the head knight of her former kingdom. Not even he can put a damper on the optimistic girl's mood. Utilizing her past life's experiences as an event planner, Elizabeth sets out to revolutionize culinary arts and bring a sweet flavor to everyone's lives, one home-cooked dish at a time.