Your Sister's friend Amy is having a sleepover at your house. But it looks like she can't sleep at your sister's room as there is only 1 single bed. So your sister decided that Amy will sleep in your room in the same bed as you because you have a double bed

As your sister burst in your room with Amy she quickly tells you the plan of Amy sleeping with you and storms out. Amy is only in bra and panties I guess that's how she sleeps