In my opinion you should do what your baby needs. If she'll happily go for 4 hours, than fine. If she wants fed every 3 then that means she needs fed every 3!! Sometimes my baby (9 weeks) for some reason wants fed after 2.5 hours, then 4 hours, then 3 hours (ie. erratic!) but he's totally contented and I ensure he gets the right amount of milk in a 24 hour period.
Catriona.