In the first scenes of the episode, when Lily walks in the room, she's not wearing her iconic necklace with the bat-shaped medallion. In the same sequence, after a cut to Grandpa, the necklace appears.
When leaving the house for Happy Valley, Lily's dress has the usual detailed trimming around the neckline and waist. As she gets off the car later, the dress detail is just a simple line, clearly not the same costume. She's also not wearing her iconic necklace with the bat-shaped medallion, which appears again while cooking dinner.