Order her around.

Her plan was going very well so far, so why shouldn't she just keep at it? She looked over at Yeria and slowly hitched her skirt up around her hips so that her bright red thong under it was clearly visible to the girl. "I think you want a taste of this don't you?"
Sirena asks, but before waiting for a reply she says, "Get started on it then." Her tone left out any real room for argument but she watched Yeria carefully for her reaction.