Go to the right and upstairs. Go through the open door and to the room where a woman sings. She's extremely dangerous - one look at your character and you'll die. Avoid running and jumping to remain hidden.
Sneak behind her back and you'll reach the bedroom. Climb the table and drop the vase on the floor - there's a key inside. Pick it up, and head for the locked door on the lower floor. Open them, enter the room, and take a few steps to the right - The Lady will appear. Light the lighter and sprint to the right, then slide through the gap in the wall.
You're safe. Proceed and you'll find yourself in the attic with some mannequins. Don't stop here, go on and you'll find a plank, which you must pull back to reach another interesting location. Pick up the mirror from the cabinet - it's your weapon to defeat the woman.