Couple of thoughts ...
Firstly, suggest you try to identify at least 3 possible experiments, so that your daughter is given an opportunity to choose which one she likes the sound of best - thus making it 'her' experiment.
Secondly, my own suggestion would be to construct a bee-oriented experiment rather than a hive-oriented experiment - 'cause you've only got 2 hives to work with, but many hundreds of foragers ...
So - how about placing a number of feeders, each containing a different solution, a short distance from the hives - then observe the number of bees drinking from each feeder at regular intervals throughout the day ?
The 'feeders' could be nothing more than ordinary saucers with a folded kitchen towel holding the liquid (to hopefully prevent drowning). The solutions could be (say): rainwater; tapwater; dilute sugar solution; dilute salt solution; dilute bleach solution; dilute nettle 'soup' - and so on. (Best to make up the solutions in bottles, so as to have plenty available for 'topping-up') Results could be displayed in either tabular, graphical or bar-chart format.
As far as I know, this would be a piece of original research, for I've never yet read of such an experiment being conducted. If I'm wrong on this, then no doubt someone here will correct me. I anticipate that the idea of doing something original would itself be inspiring.

'best
LJ