What's Appropriate in Critiquing Your Housekeeper?

Mine started today, and we like her a lot. She’s very sweet and reasonably priced. She comes twice a week so I left her a list of things to do on each day. She does not dust to my liking (dusts around most things) and I feel like if I’m paying someone to clean, I shouldn’t have to clean after them. Have any of you had this problem, and what is the most tactful way of handling it? Should I just give her a few weeks and see if she gets in the swing of things?