Alex and Lilly invite her over under the guise of interviewing and testing her for a position as a babysitter. She's dressed up as professionally as she can, even wearing slightly too big heels that she clearly borrowed from her mom.
But the girls have no intention of giving Ella a position. They instead tell her that they want her to get some experience...by being babysat by them! They will teach her all she needs to know about taking care of little ones by doing it to her. This involves spanking her bare bottom, stripping her naked, putting her in a thick diaper, and treating her like an absolute baby, all the while teasing her about times when she had accidents at school or acted like a little girl in the past.