During Brett's date with Archie, her hair is in an updo secured with a clip. From scene to scene it changes from that to a twisted bun secured with no clip.
When Brett is in the car with Archie, the seat belt over her shoulder; when the camera moves, the seat belt is around her upper arm. This happens throughout the car ride.
When Brett goes to Archie's place to tell him someone was reading her book and meets a girl who was having an affair with him, she meets a girl who was having an affair with Archie; the braces of her shirt were slipping down. But when she was talking to Brett, the braces are fine, not slipped down.
Right after the 'Sanctuary' title when Brett and her father are driving to her parents' house, Brett's seat belt goes from across her body to under her arm.