I'd look right at her and say something like...."Sounds like you've already made up your mind you can't or won't do this....I know your better than that." and leave it at that.
My Grandmartyr (yes I said marytr) acts EXACTLY like your W as far as the pity blackmail thing goes. You know what? I'm the only person in our family she truly feels close to....I'm the one she appears to respect the most....and I'm the only one who ever puts my foot down with her and calls her on the carpet about her behavior...I'm the only one who doesn't tolerate it.
Try it with your W. Tell her you don't appreciate the way she talks down about herself and that you flat-out don't buy it. Tell her you think she says those things as an excuse not to have to do them. Challenge her.
