I am so pissed off with my helper. She put baby to sleep in the cot with no bed sheet even though we had 2 new bedsheets in the house. When I asked her what the F she was thinking, she just mumbled that she didn't realize there were bedsheets (she unpacked them and also washed them and kept them away) so how can she pretend not to know?

Is this an honest mistake or is she always like this? Could it be she's having one of those days where everything goes wrong or is this a daily occurrence? If she's normally not forgetful, just reprimand her gently and let it go but if it's a recurring pattern, then maybe you can sit her down and ask her what's bothering her and causing her work performance to slip.