I have had such a difficult time believing that Mollie would run East on 385 Ave, but the incident started at 7:45 PM and the location is East on 385 Ave, so, difficult as that is to believe, it's most likely.
If we look at just that which we know, most reports have Mollie starting her run at 7:30. At 7:45, an incident regarding Mollie occurred near 1900 385 Ave. That's about 2 miles from the house-sit (rough guess). Can runners weigh in about 2 miles in 15 minutes?
That incident ends at a specific time of 8:28. I suppose that's related to heart beat, but we can't be sure. It seems a bit too specific to be something different. The body was found SE of Guernsey, and without adding anything to the story, that's where Mollie was murdered at 8:28PM on July 18, 2018.