Tensei shita Watashi wa Osanai Onna Hakushaku - Koukennin no Koushaku ni Ezuke shinagara, Ryouchi Hatten no Tame ni Bannou Mahou de Iroiro Tsukuru Tsumori desu

Martine, who by some chance remembered that her previous life was that of an office lady in her late twenties/early thirties, became the head of the counts family after her fathers death. But Martine, still a child, knows nothing about managing the territory. On top of that, because her father, the previous head, was completely hopeless, the territory is already on the verge of collapse! Finally, the time has come to use that. Thats right! Martine could actually use molding magic that could create anything!

https://www.cmoa.jp/title/342780/