well in the end, it's your daughter, and her teeth, so the hygenist really doesn't have the best bedside manner if she worded it that way. just not really courteous or good customer service (and yes, you are a paying customer).
i never got why medical professionals are allowed to act all self righteous about how we treat our bodies, teeth, eyes, whatever. they should offer advice and help and support to do the right things, but not be patronizing, demanding, or scolding.
they provide a service, we are paying for it. we don't answer to them. i don't care how many degrees you have (or how much more money you make than i do) it's my body and i'm paying you to take care of it (or fix it, heal it, or what have you).
oh yeah, to answer your question, you are doing it more religiously than we are, we do 2x per day usually but not always. my son is 5 and i supervise but he does it himself. sometimes i will "check" for him just to make sure but he does a pretty good job.