I would wake her....although now it's night time anyway so it's almost not worth it lol. With DD I never let her sleep too long (more than a couple of hours - not that I ever had to worry, she was the queen of cat napping during the day) or go too long without offering milk during the day. I felt like this meant she would sleep longer at night. I don't know if that is why she always slept so well at night (even as a newborn it was max 2 times at night, usually 1) or if I was just super lucky. I guess I will know for sure next time...