My two-and-a-half-month-old recently has been sleeping for progressively longer each night. Last night she slept for nine or ten hours straight and wasn't even crying when I woke her up. She breast-fed well when I woke her; she seems happy and alert during the day and is very playful and curious. Is it okay to go so long without a feeding at night?
While we think of young infants needing to eat frequently and waking during the night, eventually they do sleep for longer periods of time, and can "sleep through the night." The timing of when this happens is quite variable. Most babies can sleep 6 or 7 hours at night at about 3 months of age, but some learn to do this much sooner, some as early as 6 to 8 weeks. By 6 months of age many babies will sleep 9 to 12 hours at night, and this is perfectly normal -- since the infant is bigger, her stomach holds more, and she can go longer without eating at night. Additionally, as babies grow and mature their sleep cycle matures and they learn how to sleep soundly, and not respond to every outside stimulus.
This doesn't necessarily hold true for infants who have medical problems or who are underweight. They may need to be fed on a more consistent basis, even if they have the ability to sleep longer.
It sounds as though your baby is one of those content, early sleepers, and it is okay for her to go that long without eating, as long as she is otherwise well and growing normally.