I've tried letting her chase it to the point of wearing herself out, but the novelty never seems to wear off. She spends about 5 hrs a night outside chasing shadows in the yard until I bring her in too. I'm hoping it's just a strange puppy habit she'll outgrow, but it can get frustrating. I'm worried she might take to chasing headlights too. She gets totally fixated on the shadows/reflections and doesn't seem to notice I am even talking to her when usually she is obedient.

My old roommate used to actually bring her inside with the flashlight because she didn't listen to him.