My daughter has been super fussy while eating out of the nuk slow flow nipple and it takes her forever to eat 4 oz. I grabbed her a nuk simply natural medium flow bottle at Walmart and she eats it so fast she gets an upset tummy and spits up some! She did have a tiny amount come out the side of her mouth, but she had the same thing happen with the slow flow. Are these nipples too fast for her? Or does it just take time to adjust. Sorry if this has been posted before! -Thank you!