Edge her.

You rubbed her clit, teasing her until her legs were weaker, "You want to cum? To your own sister?" you teased her. She tried saying yes, but all that came out was a jumbled mess of sounds that sounded like words "Just nod. You'll look stupid." she nodded "No." you said in a tone that made Elena tense, trying to hold back.

You kept her on the edge, using your own body as practice, letting you know exactly when to stop and when you can start up again. You left her and attended to dinner, either forgetting to let her cum or you don't want her to have the pleasure of an orgasm. Your plan is making her your bitch, even if it involves taking full control over her orgasms. What she doesn't know, if she masturbates, you'll punish her. You secretly hoped she would.

She was now on the floor, not risking the walk to a chair, with her hands cuffed. You smiled to yourself "I'll be kind and let you eat." you undid her cuffs, took the blindfold off, but before you took her gag out "If you are mean to me, you can forget about that orgasm until tomorrow." you saw her nod. Seems like her weakness is her pussy, especially being edged. You took the ball gag out and let her eat the food she made, but you finished preparing.

Shortly after you both finished eating the late dinner, you watch Elena sit on the couch, she was avoiding eye contact, probably because of you edging her. Eventually she reached down her pants, but was met with a sudden impact from the crop you brought down before you confronted her "What the fuck, Emma!" she yelled.

"You don't make yourself cum. I want to make sure you get edged." you said. You watched her hand come back out of her pants "If you want to cum, then strip." you ordered.

She stared you down. You became very nervous, because the second she becomes her old self, you'll lose your confidence. She obeyed, to your surprise. Edging her must really make her submissive. You point to the floor in front of you, which is where Elena stood shortly after you pointed.