What you need is blood.

"I would like a strawberry sundae," she said with a smile. The counter boy blushed.
"C-c-coming right up, maam!".
He scurried to the ice cream machine and began to craft her item. He was obviously flustered. Three times, he ruined the sundae. He glanced back to her each time. She just kept on smiling.
He finally made the sundae properly and set it down in front of her.
"Enjoy maam!" he blurted. She giggled.
"Your face is so red...." she read his nametag. "Howard. what's wrong?"
"Nothing maam! Nothing at all!"
She giggled again.
"You're kinda funny."
She picked up her spoon and scooped up a miniscule bit of ice cream. With a seductive flair, she slowly licked the ice cream off the spoon, all while staring into Howard's eyes. He had never been in a situation like this. The closest thing was when Becky Stewart held his hand during the school trip last year. He gulped.
"Can I ask you a question, Howard?"
"Ye-yes maam!"
"Are you a...are you a virgin?"
"Maam?"
"I'm asking you if you've ever done it before. Had sex. Fucked. Yes?"
"No maam, I'm a-a-a Christian!"
"Oh. So you're saving it for marriage?"
"Yes maam!"
She looked genuinely disappointed.
"Aww. Cus I was thinking....maybe we could have some fun later.."
"What...what kinda fun, maam?"
She giggled again. Her sundae was melting, dripping onto the counter top. She rose slowly from her seat and beckoned for Howard to follow her out the door. His hear was pounding. His shift ended at 11:30, but it was still only 9:52. But this was a once in a lifetime chance. Pretty girls don't just come in and offer to have sex with you everyday. He didn't really need this job anyway. He rushed from around the corner and hurried outside.
The cold air chilled him as the the door closed. It was a December night. The sky was bereft of cloud, the full moon glowing in the distance.
She was nowhere to be seen.
Surely she wasn't leading him on.
But then he heard a whisper from behind him. It was faint, but it carried, whistling by his ears like wind. It was her voice.
He rushed to the back of the store. She wasn't there.
Instead, he found two massacred bodies. He recognized one as the store manager.
His first reaction was to throw up. The second was to faint. By the time he fought off both urges, he felt a presence behind him. He breathed deeply.
"Are you still afraid, Howard?" she asked him.
"What did you do?" he asked her.
"Having my fun..."
She bit into his neck and ripped out his esophagus. His blood was a sweet nectar.