Its likely Wilson exaggerated being struck to reinforce his story. He could've well been struck by Brown, albeit much less powerfully, but still more than sufficient to give Wilson legal ground to shoot him.In my view those photos never really corroborated his story anyway (seems very little bruising for an attack as powerful as the one he describes), but obviously as I'm not a medical professional I'm not qualified to judge. I am, however, happy to trust the guys who are qualified to judge, and they're saying that when he went to hospital there were no bruises or lacerations.
Anyway, the more important point that she's making is that within the process that led to the Grand Jury decision there were significant lines of questioning that weren't pursued as they should have been. The implication is that there's a question mark over the decision, and also question marks over the competence or impartiality of the process.
Her view is legitimate, but at the end of the day there's a slight and natural bias built into the questioning that gives cops the benefit of the doubt.