Not sure if I'm overstating, but most of us seem to agree she was taken somewhere on BSR, which makes the most sense despite the cell tower ping. Two witnesses saw her and there are no reports of her on either Rt 31 or Ball State Rd. 31 is much busier than BSR and she would have been spotted by someone. We also know (I think) police searched the site and seem to have focused on the cart path, where body was found and some evidence of burning exists, as well as the junction at Connor Lane, Boylston, Radford, and BSR.
A car driving along BSR and taking her seems a little problematic. If this was planned, for a car to wait on BSR would be odd and someone would likely notice. Even a car pulling in or out of the cart path twice strikes me as problematic because of the risk involved. There isn't a ton of traffic on BSR but there is some. One scenario I wonder about is:
The killer knows she runs that route on Sundays at around 1ish before she leaves. He also knows she's home that weekend. So he parks his car at the cemetery, which is out of sight to anyone but a person visiting it (it's a small cemetery and can't be that busy; I've been there and seen no one). He takes his accelerant/blowtorch/taser/etc and cuts through the woods about a half mile to the cart path, where he waits for her to walk by, because she usually walks at the beginning of the her runs. She's got her headphones on and isn't on guard, like she would be in the city. She feels safe and he surprises her, silences and/or incapacitates her, drags her down the path out of site, kills her, etc, burns her post-mortem and leaves the body to be found. This could all be done fairly quickly.
He then cuts back through the woods to the cemetery, gets in his car, pulls into the road and drives off. Like the cemetery, Connor Lane is extremely quiet. There is only 1 house set back from the road. Then there's the cemetery on the opposite site at the end of a little drive. You can't see most of it from the road. At the end of the Connor lane is an open gate that looks like the way to a single house (not sure if it is or not). Even if by some odd chance someone sees a car pull onto BSR or Boylston St. from Connor Lane, they're probably not going to pay much attention.
It's a risky crime and this strikes me as the least risky way to pull it off. Maybe? The biggest risk is the fire and maybe that's the signature. There are easier, more effective ways (bleach, for one) to destroy DNA.