I was referring to the Groundhog Day incident. Harry probably isn't aware of it, but could come across it by asking simple questions of Hermione like "why were you so angry that day of the battle?". Hermione seems aware that she is missing memories here, due to her "lost track of time" statement to Susan.

Thinking of what Draco might have done to her and then obliviated seems a reasonable explanation for her anger towards him during the battle, and perhaps why she can believe that she did attempt to murder him.