Someone (male or female) who is keeping track of events in order to use them in future arguments. The CartLady is a poetic vision of a librarian going around with an old screechy cart loaded with huge books.
Once again Joe reminded me of the time I borrowed him a black t-shirt. That was six months ago! What a CartLady!
The crack head lady you see pushing a stolen grocery cart with all fo her b elongings...talking to herself.
That cart lady is on crack.