I think that info came from her phone vs. mom providing that information herself, for a couple of reasons:
1. Remains were found very quickly after JSO arrived in Alabama and began searching. I think they had a pretty good idea of the locations to search, specifically, beforehand.
2. Didn't mom say she had recently begun taking Taylor to Alabama for her grandmother to watch her (which grandmother later confirmed was NOT true?)
I'm wondering if LE either had the phone location info then and presented it to Brianna and that's the excuse she made for it, or, realizing that they would be acquiring her phone records/locations very soon, preemptively gave the "drove to Alabama for Grandma to watch Taylor" excuse in an attempt to explain away that trip beforehand?
I'm babbling now, basically in short, I think Brianna's phone locations told THE location, not Brianna. She has given too many false statements for me to think otherwise.