Suggestion:
I would just let her continue to nurse as long as she needs to, regardless of whether or not she's actually feeding or just sucking for comfort. Comfort nursing is actually a very important part of the feeding process. Not only does it help bring in small amounts of fatty hindmilk, which is necessary for proper fat intake, but the extra swallowing aids in digestion. Comfort nursing also helps build your milk supply to meet your babies needs. All of baby's sucking needs should be met at the breast at her age. It's best to avoid pacifiers and bottles until breastfeeding is well established – around 4-6 weeks of age.
If she's really snoozy at the breast, try doing breast compressions once her swallowing slows down: http://www.nbci.ca/index.php?option=com_content&view=article&id=8:breast-compression&catid=5:information&Itemid=17 That will help stimulate the flow of your milk so she'll start feeding again, and she'll also get more hindmilk that way.
Here's some more helpful links for you:
Frequent Nursing: http://www.kellymom.com/bf/normal/frequent-nursing.html
Comfort Nursing: http://www.kellymom.com/parenting/sleep/comfortnursing.html
Cluster Feeding: http://www.kellymom.com/babyconcerns/fussy-evening.html
What should I know before giving my breastfed baby a pacifier? http://www.kellymom.com/bf/start/concerns/pacifier.html
