She is furious

Cindy was blinded by rage at this point. Sure, she made mistakes and all, but that's just not fair. All what happened was her sister's fault, she would be tied up in the basement while her sister would laugh and have the best day of her life. Until dinner was like eight hours, that was way to long! And all that just because Cindy's stepmother wouldn't listen to her. She had to somehow end all this, but how? It was still no solution to run. She had a hard time dealing with all that, but she would not let her father down. So how should she stop it? Or best turn it on her sister somehow. "I can't believe you already set a new record, you little brat" Cindy heard her mother's voice coming from downstairs. "Yea mom, she isn't even able to follow the simplest rules." Brenda said with a smirk, grabbing Cindy's arm to make sure she would not escape. Cindy tried to escape her sister, but there was only the one way out of the bathroom. She was dragged down into the basement by her sister, unfortunately she was much stronger than Cindy. "Don't let Collin com down here, it's not for his eyes yet." Her mother said and went to get the box with the bondage utensils from earlier while Brenda held Cindy down on the dirty floor. "Hopefully this will be you a lesson to finally remember the rules!" her mother said, and began tying her up. She started by putting on the ball gag and the blindfold. Further, Cindy could only feel how she got led into a room and put on her knees. "The company has also sent us some bigger devices. They knew we have no experience in tying somebody up, so they gave us this simple thing here to lock you up." Cindy had to go on all fours, her neck getting locked in something like a collar and her hands in metal cuffs. Her legs were also put into cuffs so that her ass was up in the air. Saliva began leaking out of her open **** mouth, running down her chin and dropping on the floor. Finally, her mother finished and Cindy could hear her say, "At least for the next hours you won't be able to cause any troubles. Your sister will come looking for you every hour to make sure you're alright down here." After that, she received a few slaps on her ass, and she could hear them both starting to leave. "I hope you have a good time little sis" Cindy could hear her sister say, followed by the slam of the door.

Cindy tied up and locked into a metal frame in the basement.

This picture was quite problematic, but I managed to get close to what I wanted.