When I was about to sleep, I’m almost finished the first manga volume of #私の推しは悪役令嬢 and well, the first volume only covers the first half of the first chapter in the first volume in the light novel. Looking at the wiki pages, it will take 5 manga volumes to cover the first volume of the light novel. I will finish the first volume today most likely.
On the flip side, the manga version is a lot easier to read and has furigana. Probably you only need lower intermediate Japanese (JLPT N3) to understand most of it compared to the light novel counterpart.