Honesty is a core value

Why can't people just be honest? With me and with themselves.  Every time I think my assistant is improving she does some dumb stuff that makes me want to rip my hair out. When I hired her I told her what I needed and she ensured that she could deliver. When I ask her to do something she either totally doesn't understand what I need or totally blows it off. I keep finding crap I asked her do months ago buried under piles of papers or not even started. Even when I follow up with her to see how she is doing on something she either 'forgot' or is still working on it. Mind you, this is stuff I asked her to start months prior. I wind up doing most of it myself. Some of it is slightly challenging so she can learn how to do it, but even the really simple mindless stuff is getting pushed off. That is so frustrating because I need the stuff done. What does she think, that the stuff is going to go away because I don't ask her about it every single minute of ever day? When she does stuff on her own without me checking it, it is wrong! Arg! I am so done! I really don't understand how someone who is almost 30 could be so clueless. Then I wind up being the bad guy because she is so nice. After working with the girl I worked with last year, my expectations are high. She was so intuitive. She would do things that I never even thought about! There are so many things that I haven't been able to do this year that I was able to do last year. How long does it take you to find your groove in a new job? Maybe I'm  being unrealistic.