M.C.
She could also be going through a growth spurt, and need to increase your milk supply. If this is the case, it should go away in a couple of days, once you're making more. Or if there have been some kind of unexpected (for her) changes in your life, she may be looking for comfort. I went back to work part time when my DD was 4 months old, and the first couple of days, when I got home, she would nurse and let the milk run out of the side of her mouth--she wasn't hungry, she was just insecure and wanted mommy! After a few days she got used to things, though (she always stayed with her dad while I worked), and we went back to normal.