It was a while ago now so I can't remember exactly how old he was but my DS went for 12 days with no poo a few times!! It was a few months pre-solids and fully breastfed too so maybe 3-4mths and the mchn said Drs won't really worry until after 14 days unless he seemed distressed by it. If her tummy isn't sore or swollen when your massage it or cycle her legs, and she doesn't seem to be in pain I wouldn't be too worried. Breastmilk is perfectly formulated for them to digest and she is obviously using every bit she needs!!! Waiting for the explosion is the worst bit although my DS went 12 days then did a normal sized poo then another 10 after that once! Unreal!

ETA: My mchn recommended the sugar too do it must be a common way to make them go.