There are several reasons why you are faster on your bike than your daughter's. These may include the overall weight, weight of the wheels and tires (especially when you're going up the hills), tire rolling resistance, resistance of bearings in the hubs and drivetrain, and aerodynamic drag. There might also be some major inefficiencies related to bike fit (it's hard to ride well on a bike that is too big or too small for your body). I suspect your bike is better on every one of these points. There may not be big differences in some of them, but every little bit adds up.