Lethal dumped AJ basically out of paranoia because he feared she would start fukking around on the road once she joined the E. From what I and most of us know, that has not been the case. This is more compounded by the fact that I believe either he was about to propose to her, or they were already engaged at the time.
Barreta apparently cheated on AJ, and one of his ring rats let her know about it. Of course, AJ got pissed, and they broke up. which makes this GIF:
Hilarious in hindsight because of their past relationship, and also because of the fact that Trent was released a few days later.
I get the feeling that AJ kicking her feet up at him was not supposed to happen, so I guess she still had some harbored feelings against him, and wanted to that to him as a parting 'fukk you' before he was released.