I'm going to feed off of this idea and bring up something very grim so if you're not in the mood please skip past my comment.
What if Jayme was able to hide for a bit because she was in her room with the dog & the door was shut. Or even if she wasn't able to hide.. could Jayme have been able to escape after being injured? What if she wasn't the target, her parents were, but she was able to hide long enough to call 911. As she is making the call she is attacked and the police hear that commotion. What if Jayme was able to flee the scene and with her adrenaline pumping was able to run fast enough and far enough away and find a really good hiding spot and perished from her injuries there? I know dogs have been out but dogs miss their targets sometimes. They really seem to be focusing on the local area and have really only done one single significant search. But with cold temps and falling leaves she could be hard to find in some of the wooded areas? I don't know, just an idea that might not make a lot of sense.
That makes the presser with her aunts even more confusing but its just something I was thinking about with the whole speculation that she could have been hiding. I still lean towards the suspect being known to at least Jayme, possibly her family too, and I hope that she is alive somewhere.
Let me suggest a variation on that. Jayme makes the call, then escapes out the back. As she's going out, she hears the perp (who now knows he's out of time) shoot her mother and possibly her dog. (He didn't shoot the dog, but she doesn't know that.) She runs into the woods, and can't find her. Perhaps shouts some threats.
Now, Jayme is alone in the woods, in the dark, and may feel that in trying to call police and/or escaping, she's gotten her mother and dog killed. Further, the perp might be someone known and trusted by the family, or it could be someone she sees as an authority figure. (If the guy had a scanner, he could have been a fireman - for that matter, he could have been dressed as a cop.) At any rate, she is terrified, feels guilty and has no idea who she can trust. Is there any remote chance she might be in hiding, maybe with a teen that she knows from school or activities helping her by providing food, blankets and/or a hiding spot? Could that be part of the reason for the aunt showing the dog and saying he missed her?