Yes, that's crummy that she said anything. I'd put it up to the well-oiled aspect and maybe she was wishing for a bit of an argument with someone and you happened to be there :-)

I have an aunt who constantly changes around her will, sometimes I'm in (in last place) and a year or two ago when my wayward cousin (my aunt's brother's daughter, not her own; my aunt is 87 and never married) decided to show up again (she disappears for 5-10-20 years at a time) she was "needy" so my aunt put her in the will and that meant I was out since I'm not so needy.

I would think of it a little bit like that; maybe she sees your brother as more needy than you; that you can take care of yourself better and have it more together? With giving things away, it's never going to be "fair" because our ideas of fair and other people's usually don't match. Even when people get the same amounts there will be problems with little personal effects, someone getting something another wanted, and all that.

Do you know your mothers' will/estate? It could be that there is a "surprise" in there for you and at the moment, when she's getting her aunt's money, she's only thinking of your brother because he is, at the moment, "there" in front of her often. Some people are shallow like that and can only see what's in front of them. Too, I'd keep looking at the well-oiled aspect; who knows if she'll do what she says and who knows if she'll even remember it, etc.