I do think the investigators know this about her. After that initial interview where they confronted her about the lies and she just immediately came up with excuses - no emotion - and when they played “good cop/bad cop” and the good guy complimented her and she laughed and just went along with the line of questioning, they knew then that she was a sociopath.
They probably see a lot of them in their line of work, more than you or I would normally..........