You need to do everything in the yard before you talk to Violet.
She'll come out, but as long as you don't talk to her, you should be able to finish looking around.
You probably don't need all of this, but here's a list of everything you can do in the yard.
Look at the graffiti
Look at the flagpole
Look at the head next to the flagpole
Look at the walls (on the gate)
Look at the barbed wire on the walls (I can't remember exactly where this was)
Talk to AJ & Tenn up on the tower
Examine the wooden spear barricade
Flip over the picnic table
Talk to Mitch
Look at the burned out building (rubble)
Look at the pile of heads on the ground
Look at all of the graves (Marlon, Brody, Ms. Martin, etc.). I did not spit on Marlon's grave.
Make sure to pet Rosie for:
Shoot the bow with Louis. Don't miss for:
If it hasn't popped yet, make sure to look around one more time for anything you can do. Once you talk to Violet, you can't go back.