She could be the reason why this all started.

"You met with Elena here, a few months ago, didn't you?" you asked, trying to look intimidated.

Either Sarah was intimidated or saw your attempt at it fail and wanted to play along "Yes. I didn't mean for her to become so mean to you."

"And you were masturbating when I came to pick you up." you said, remembering that moment clearly.

"To the photo Elena sent me." she said "Are you trying to Domme me?"

You grabbed her neck and pulled her in close "Is it working?"

"I could make you submit in two seconds, but you did see me masturbate. To your photo, so...I'll play along with you trying to Domme me." she said, but you can tell she'll probably get bored and make you, her sub instead.

You kissed her again, but this time you placed a hand on her pussy "I want to see this in my bed." you said. Now that you had gotten it off your chest, you had a new found 'strength' that made you more forward, like you were when you made Elena your sub. But this time, its love. You turned your love into domination, taking control of Sarah, despite she having the power to **** you into submission.