Thinking back to the BC Vamp spell, since its outright there and presuming Mavra knew it, she was being truly deferential at the moment then... I was always wondering if she was playing a game or what not... but that would also suggest that she now has to take Dresden out due to the threat level he represents to her going forward...
If she's aware of how risky it would be for him to actually do, she can probably guess he's not going to hat up and use it unless pressed. I figured there had to have been some downside to Harry actually using it, or he would have just opened a can of whoop-ass on the BCV's in It's My Birthday Too instead of sneaking around backstabbing them with gravitus and spitting garlic on them.
So Mavra probably thinks she can leave him on the back burner for the short to intermediate term, but taking him out is going to have to happen before she starts making any big moves that would really piss him off.
I also kind of want to know which of the crack theories really bothered him.