My vote goes to overeating. When you are feeding her the second time later in bed, do you switch sides from the one you fed her on earlier? If all that particular session seems to be about is comfort sucking, then you could always stay on the same side you nursed her on before, and if she has emptied that breast, she will be sucking on a fairly empty side and probably wouldn't get as much. If she seems happy and content and otherwise doesn't notice I wouldn't worry about it. I remember when my DD projectile vomited the first time. She actually also smiled for the first time while awake after that, while I ran around like a chicken with my head cut off freaking out. Sigh.