I'm currently working on my MSc thesis under a PhD candidate's supervision. She has very recently published a paper as first author in a well-known journal where she claims to have followed methodology used by her colleagues and co-authors (in their other papers). However, I know that this is not true and that the PhD candidate is fully aware that she's lying too. I know that she has lied because the thesis of MSc students who worked under her previously state something entirely different from what the PhD candidate has cited as source in her paper.

Question: What I don't know is if this act qualifies as scientific misconduct and/or how severe this is. If yes, then what is an act like this called?

Some of the differences between the methodology she has actually used, and the one she claims to have used are minor. The issue is that there are so many of these "minor differences" that they might end up having major influence on the results. e.g for how long samples were centrifuged, rpm of centrifuge, temperature settings of gas chromatography machine, etc.

The major (?) difference pertains to composition of nutrient broth (microbiology) which I'm confident she has never even prepared throughout the course of her PhD.

Unfortunately, it's clear to me that the PhD candidate's supervisors don't care about this since they seem to be working in tandem to increase each other's h-index. So, reporting to them won't make much of a difference. But for my own sanity, I would like to know just how big of a deal is this kind of act?