Pretend
Sofia tiptoed and went back to her room to plan her next move. Once her father will approve of her sister's decision to imprison her in the basement, she will lose a chance to escape!
She quickly went to the closet, grabbed her bag, and filled it with her clothes and important stuff.
She's ready to escape anytime if the opportunity arises. She hides the bag inside the closet.
The day is long, she will remain in her room sulking and only get out during mealtime.
Tonight, when everyone was already sleeping soundly in their rooms, she will leave the manor and escape!
Everyone can get out of the house, but they are prohibiting it now due to the fear of being followed by the enemy back to the manor. Based on Grandpa Terros explanation, the invisible shield will only react if it can sense a foreign being or entity trying to enter the vicinity of the manor.
This means it's safe for her to leave and also safe to come back if she wanted to!