Someone Ally knew does not necessarily equal a love interest, family member, or even a close friend. She could have had a stalker that she didn't even know she had. She could have had a coworker who was obsessed with her, but she didn't know it. And even though the houses are in a rural area, she could have had a neighbor who was watching her and knew her jogging pattern and route.
The fact that she was shot from behind makes me lean away from someone really close to her because it's so impersonal. Many people who kill their girlfriends, wives, children, etc. make sure the person knows who is killing them. It's another level of showing the victim who is in control, I suppose. The person gets their final revenge and the victim dies knowing who their killer was.
I just can't rule out a random killer or someone who knew Ally, but not well.