"do [something] now". How to interpret this?

I am not a native English speaker, and for some reason, when my superior at work tells me to "stop what you are doing, and do this now" through internal channels online, I feel it has a negative tone to it, as it's commanding.

I specifically don't feel comfortable with the word "now". There is no life-death situation to use it. I feel like she is giving me orders like a child. Like "do this, NOW". I think saying "stop what you are doing, and do this instead" has a more positive tone to it. But since I am not a native English speaker, there is a chance I am not interpreting the former sentence the right way.

Is it normal to say something like that ("stop what you are doing, and do this now") to someone with the intention of being polite and by using the right words, or it can be intentional to convey that she has power over me as my superior and I am her subordinate, and I have to obey?

The request is direct and thus may be perceived as rude. To think about the statement more clearly, it helps to consider a few factors.

Imperative mood

Do this now is an imperative clause (ThoughtCo), which conveys a command or request that you comply immediately. The use of imperative mood is more direct, which depending on context (see the third factor) may be perceived as less polite than making a request in other moods, e.g.:

Would you do this now? (indicative mood)

I think you should do this now. (indicative mood)

I wish this were done. (subjunctive mood)

Function words like please

The statement can also be made more or less polite by what you add to it. For instance, please (Merriam-Webster) is a function word that makes a request more polite. That is one tool that could slightly mollify the demand made:

Please do this now.

Would you please do this now?

I think you should do this now, please.

For an example of a much ruder addition, consider this:

Fucking do this now.

Context and Now

Now makes the demand more immediate, which may be rude in contexts where the addressee has other tasks and obligations. Rudeness with a word like now is going to be circumstantial and heavily dependent on context. For instance, in an instructional space like an ASVAB test, the administrator might say:

Now look at the section of your answer sheet labeled "PRACTICE”. Notice that answer space C has been marked for question S1. Now do practice questions S2 and S3 by yourself. Find the correct answer to the question, then mark the space on your answer sheet that has the same letter as the answer you picked. Do this now.

The clauses are imperative. The context is one where imperatives for the sake of test instructions are expected. The now clarifies that students should act at that moment, and is not a sign of rudeness.

So I wouldn't read now as something inherently rude, but would think about that carefully in the context it's delivered in.