How much is too much when feeding with bottle?

vszapp

I just started back to work last week, so we're still figuring out how much DD takes from the bottle. I thought she was eating a lot so far, averaging 4oz per bottle, and taking 4 bottles while I'm gone. She nurses once in the morning and at least twice at night. So that's 7-8 feedings, with 16oz coming from half of those feedings (no idea how much the rest are since I nurse her!). 

Now today the nanny said she's been starving and has taken SIX bottles in 8 hours (total of 20oz). Plus I already nursed her this morning. Should the nanny be cutting her off? Or is this just a growth spurt? Allegedly DD will just keep on going no matter how much is in the bottle. I'm worried about over-feeding her but also don't want her to go hungry...