It seems to me , too , that the bag of finger bones is the one significant stand-out. You know...one of these things is not like the others..

..the others being just generally the type of items that could be used.
I do think she's got them , but probably hasn't used them yet. The really influential actions Davos has taken to date still seem too much like Davos , too unrelated to Mel's agenda ( as far as we can tell ) to be Mel's glamoured agent. It would not have been in Mel's interest to spirit Edric Storm away , and it's Davos who would know that once Stannis was aware of the letter from the wall , he was likely to do the right thing.
Mel tells Stannis what he should do..then works to convince or manipulate him into it , usually by arranging some "proof " of her power. Do we really think any of the reported deaths were the result of her burning leeches, or were the leeches her way of taking credit and pulling Stannis further under her control ?
Davos, OTOH , just points out the salient facts and trusts Stannis ,with his rigid sense of justice , to make the "right" choices. As in the case of Edric , if he feels Stannis is going to choose wrongly , and Davos has any way of preventing it , he will..even at his own risk... In that instance, he seems to have been acting not only to save Edric , but also to save Stannis from damning himself further.
Stannis didn't need to be told to head North , he's enough of a tactician to see the value in it..once he was aware of the situation - while Davos seems too much like himself to have been Mel's agent since the Blackwater . No-one else would have written the letters to his family from White Harbour.
She may well have reason to believe he's still alive , though , or some other reason to think they could still prove useful.
And I don't think we'd have been given a Davos POV ,if it was really someone else, without making it clear within the text..as GRRM does with Reek.
Edited by bemused, 09 March 2012 - 02:50 PM.