I'd been wondering for such a long time whether she was aware of his story pre-trial. Because of the looks on her face all the time I decided that she didn't but that Carl probably did, even if they didn't know the whole story. I must say I was really surprised when she was in the video. So if she's known all along, why on earth was she crying all the time? IMO it can only be that Nel destroyed his version so utterly and now she's really scared that he may be going to prison.
BBM...IMO she was crying both for OP and the realization what the real truth was.