Concurrence

"...Yes, Young Lady." Riley politely answered Big Sis's question. For my mother, I would use any means."

Naturally, most likely, any child would do anything for their parents, and so I would. Her mother was suffering from a deadly disease, so Riley would burn the candle at both ends for her mother's wellness, to the point of selling her body. 

"You really would, huh. But do you even have experience with that thing?" 

"In all honesty, I have never been in a relationship yet, so I have never engaged in any sexual activities..." 

Soon after Riley's confession, Big Sis glanced at me to subtly confirm something, to which I answered her with a nod. My sister had known some of my skills and their abilities, including the Purity Sensor. 

That meant that Big Sis asked for the credibility of her claim. In the eyes of a unicorn, Riley was giving off verdant effulgence. Therefore, Riley was still a pure maiden.