maybe i'm mis-reading what you've posted, but i grew up in an area like this and was a runner so maybe this will be helpful for people who don't run:
mollie is 20 and runs several times per week. we've all seen her and she appears in pretty good shape; a very typical running schedule for someone like her who wants to run in the evening several times each week, who isn't training for races, would be something like half an hour per run, or around 3 or 4 miles. it's been mentioned somewhere that she has 3 or 4 regular routes that are probably slightly different so she can do a couple of hills or one of them is her weekly long run of maybe 6 miles, but also just to break up the monotony of running the same route through farmland or this tiny town every day. i will also bet that she starts her run and does 1 loop back home rather than running a couple of laps past home for that same reason: it's boring to run along with nothing but fields beside you (running outside in really boring surroundings is literally more tiring in my experience) and she wouldn't choose to pass the same point more than once.
at a typical workout pace, mollie would be running 7 minute miles; a hard pace would be approximately 5 minute miles. this witness is 9/10 of a mile from where she starts/finishes her run, according to a post above. if she's the type of runner who wants to finish her runs strong (something that's always coached so that runners don't get lazy at the end of a workout), she could be aiming to do her last mile in 5 minutes.
so this witness 9/10 of a mile from her start/end point likely saw her within 5-10 minutes of the beginning/end of her run. if he saw her running home at 8pm, she could have been in her driveway as early as 8:05pm.
of course, that doesn't include any cool-down period, which could be when the other witness reported seeing her walking and using her phone. if you run properly, you'd do your half hour workout, then walk/jog for maybe 10 or 15 minutes to cool down before going inside.
