I still hold that she had a general meltdown because of a LOT of things. I feel like she was forcing herself to be a bouncy castle in OoTP, and when that ended up not working out so well for her (between Sirius dying, a few other Order members being killed and Remus going off to spy on the guy who tried to kill him when he was three), she just sort of... deflated. I thought the end of HBP she kind of kicked her own ass back into shape. But maybe that was wishful thinking.