I think there is a difference between giving a child the courtesy of explaining WHY they are being requested to do something and spending an hour justify yourself after the fact (but sometimes you will have to do this). I don't think giving a child a reason EVERY time you tell them to do something makes you weak. I think it shows respect for them and makes them a partner in achieving goals. It also makes them more likely to do what you want when you are not around and helps them develop good judgment. It also helps them recognize the natural consequences (realized or not ) of NOT doing as you tell them.
Ideally, you would let her help you or explain where she needs to be so as not to be in your way. If you really need her in another room because you have guests coming in 20 minutes or something, then tell her that.
