<em>Only 1 real error, as usual well written, constructed etc. Here are a few suggestions of some expressions which I don't think a native speeaker would normally use.</em>
I noticed that she didn't even know the correct way to place cups in front of attendees although she must have done the work dozens of times during her one year's career
<em>Work is possible but because you are emphasizing something specfic I would prefer 'job', 'task' or something general like 'this preparation'.</em>
When I asked her to help me print guests' names on a piece of paper to be fit into name plates, which, again, was her regular work, instead of producing the exact measurement of the paper at once, she had to rummage her drawer to find the paper sheet that she cut before to make sure about the size.
<em>had cut - would make the time sequencing clearer.</em>
<em>I would have said 'rummage in her drawer' as she didn't necessarily rummage the whole drawer. But the choice of verb is excellent and describes exactly the situation.</em>
I have high a lot of respect for a person who performs their work with commitment, however trivial their work may be.
I also believe that however small a task seems to be, there's always room to improve.
<em>The usual collocation is - 'room for improvement' </em>
If I were her boss, there's no way I would promote her, because a person who doesn't devote her heart to trivial tasks when she has no other big business to mind, will not devote her heart either to any work entrusted to her.
<em>'Big business' is normally used to refer to very large companies as opposed to small local ones. I would have used 'important' or maybe 'work' instead of business.</em>