In the scene at Club Silencio, Betty find the mysterious blue cube in her bag. She and Rita rush home in a cab to unlock it.

On the way to the door, Betty is carrying the cube in her hands. She must have left her bag back at the club, or in the cab, it seems, because she doesn't have it with her.

They get in the house, and Betty pulls the cube out of her bag, which is now on her shoulder.

Meaningful, or a continuity error? Thoughts?

There's no continuation error. She carries her entire purse in her hands on the way to the door.