I'm not sure if this has been posted/discussed on here but this may open up another angle.
http://wlfi.com/2017/02/23/cyber-forensics-perspective-on-the-double-homicide-case/
If she was on SM maybe she was extra cautious about what she did. But after a while she may have become relaxed because things discussed in the course never happened. Maybe she got to the point where she was confident in the way she was doing things. Could this have been a SM meet up? Could it have been one of many? Always with a friend or two? Following some safety tips but not all.
Think about it. We were all young once and when someone older told us this or that and nothing ever happened to prove them right we ignored it or became relaxed after a period of time.
The FBI site lists the height & weight of Liberty and Abigail.
Liberty
Abigail
Someone upthread posted that there were different dates of death in their obits. Maybe, just my opinion, he attacked Liberty because she was the threat to him. She is listed as 5'4" and 200#. While Abigail is 5'4" and only 100#. Again just my opinion but I think this may explain deferring dates. Maybe when he left, if he left, Abigail was still alive. Maybe he left and came back? .... the events that may have went down when thinking about this. What a sick !