I would like to know who it was also. Because what I would like to know is whether she met the friend at the casino meaning Denita drove on her own back and forth, met the friend somewhere in Illinois and the friend drove to the casino in Missouri, or met the friend somewhere in Illinois and Denita drove to the casino in Missouri. Knowing that could provided some insight as to whether or not there is a witness to her whereabouts up to a certain time on the 25th. Or, of course, if that friend would be the person of interest.
There seems to be only three players on the court.
(1) The last person to claim to see her alive. This was also the person to report her missing whose story we know must have changed or LE doesn't believe it.
(2) The last person to see her alive other than the person who claimed to have last seen her alive i.e. the friend that was at the casino.
(3) The person she was divorcing.
So knowing who the friend was and what they know would be helpful.