The back door being cracked open was your first clue. A wave of mild panic washed over you, draining the blood from your face as you looked around the kitchen, nervously. You didn't know where, or when, the attack was going to come, so you were quiet as a mouse, desperate to hear any sound or noise, just to get a moment of preparation.
As you put your back up to the wall, you realized she was crafty. FAR too crafty. She had only stolen your house keys once, yet that was the only time she needed to. The fact that your booby traps didn't go off makes you realize she just had a copy of the key made. Classic. You didn't think she was smart enough for it. You carefully sidle along the wall, looking out of the corners of your eyes to see where she might spring from.
You get to the stairs. She's crafty, but not careful. Mud tracks climb up to the second floor, and you follow them, doing your best to remember when steps squeak. It's a slow process, but if she's lying in wait, you know she won't be going anywhere. Climbing to the top, the faint smell of iron, which confuses you at first, but as the faint tracks head into your bedroom, your eyes grow wide with worry. If she was able to duplicate all of your keys, then...!
You give up stealth. You burst into the room, only to gag immediately, vomiting into the hallway as your brain tries to process what you've just seen. There were two bullet holes in the walls, both opposite sides of each other. The Colt Python lying next to her was inside of a lock box, you're sure of it. You had taken it out of your gun safe to get the lock work re-timed. It naturally wore down over time, and the scars on her hands showed where the propellant had burned into her hands before the chamber rotated properly. She had dropped the gun in pain and panic, and it misfired. Guns are not a toy to just play with in real life. You told her that yourself. She simply laughed it off.
Without a jaw, Janna won't be laughing anymore.