The only source I have seen for Joleen Cummings last being seen at 5pm comes from Jennifer Sybert (Kessler) - this comes from the Arrest Affidavit. I don't consider her a reliable source. Is there some other source, such as seen by someone else or on video? If it turned up in a news story and cites a source other than Kimberly I would be interested in seeing it.
My impression was that Kimberly and Joleen were working together until close on Saturday the 12th. We know that Kimberly's car was very likely at Tangles when she dropped Joleen's car at the Home Depot. Kimberly was seen walking away from Joleen's car and toward a Gate station where she got a taxi that took her to Tangles.
Link to the Arrest Affidavit on my Google Drive for those that haven't read it.
SybertArrestAffidavit.pdf
It doesn't seem likely to me that the murder occurred anywhere but at Tangles. That is where the crime scene tape was and crime scene folks were processing for more than a day.