The Witch Medea

From Stage Storm:

After her parent's deaths, Lili is adopted by her uncle and aunt who treat her like a servant. The girl has the same dream every night, a castle covered in fog. When she's going to turn 18 her aunt and uncle decide to use an old castle as a hotel. She discovers the castle was her parents's inheritance and it's the same castle she sees every night in her dreams. Wandering the castle she finds a deserted tower with several portraits of a beautiful woman. She was a cruel witch who was beheaded after killing 200 girls from the village. When she goes out the room she starts to act in a different way...her cousin Caroline who always bullies her gets injured and several accidents happen in the castle repairs.

The bunko edition includes 2 short stories: Ningyou no Haka (A Doll's Grave), which was previously published in the second volume of Shirayuri no Kishi, and Victoria no Ishou (Victoria's Farewell Note).