Does anyone know the title of a story that's about, where the MC is kept hidden by her ste...

Does anyone know the title of a story that's about, where the MC is kept hidden by her step mother, and she always bullied by her step sister too. She can't attend any social gatherings because her step mother and step sister, made it look like she has a mental problem. But an opportunity came when the prince visited their house. The prince was the fiancé of her step sister. I can't really recall what's the story about, that's all I can remember.