In this circumstance I am a fan of the idea of a "sleep reminder," which I first read on an internet bulletin board. A sleep reminder is something that will stop your baby from playing and indicate that it is nighttime. A sleep reminder has two related goals:
- Get your child to stop playing and sleep.
- Continue to promote independent sleep, if that is a goal for your family (which it is not for all families).
You do not want to intervene unnecessarily to help a baby to sleep, but you also do not want to encourage long night wakings. A sleep reminder is an intervention about 20 minutes into a happy night waking that does something to indicate that it is sleep time. It might be placing your child in her usual sleeping position if she has moved, going in and shushing her, getting her drowsy and replacing her in her sleeping location if she goes to sleep from drowsy-but-awake, etc.
As babies get older a sleep reminder may involve frustrating the baby slightly to keep them from playing so that they go back to sleep. I realize that it sounds odd to intentionally frustrate your child, but it is the same principal as quietly walking an older toddler back to his or her big kid bed when he or she wants to get up in the middle of the night. The toddler being walked back to bed and the baby being reminded to sleep might not appreciate it, but it is for the child's good. So for example when my older infant is having a long wake-up I will go and place a pacifier near her but not pick her up. She gets frustrated that I am not there to play with her, cries out in protest for maybe ten seconds, then places the pacifier in her mouth and goes back to sleep.
Another thing to note is that a long and happy wake-up at night, in the absense of signs of overtiredness, may be an indication that your daughter is ready for more hours awake during the day and is currently experiencing what Richard Ferber calls the "too long in bed" problem.
If your family is not focused on promoting independent sleep in your child I would encourage some form of helping back to sleep after 20 minutes or so of a wake-up, but not necessarily before. Consolidated night sleep is valuable for infants.