When the guys kick in the motel door, the hooker sits up, covering her chest with the sheet; she is clearly seen as wearing a blue halter dress, rolled down to her waist. After a quick cut-away, as she gets 'tipped' and told to leave, she is still holding the sheet up to her chest, but now the dress is all the way up, covering her previously bare back, with the halter strap in place around her neck. She had no time to pull the garment into place, so the scene is obviously from two separate takes.