I won’t put words in Salarta’s mouth, but I believe the poster was saying what she was originally intended to be. Magneto’s daughter divided between his way and the X-Men was undone and she was a very different background concept for the next several decades.I agree that she was created to have conflict with the ideas of Xavier/Magento but as you said she's mostly been on Xavier's side. Unless mind controlled or possessed. That says to me that she, at her heart, is a hero not a villain or anti-hero. I think we're actually on the same page there.
Because her parentage was undone she was functionally treated as a different character then she was in the storyline above until her Genosha storyline started a move back to 60s concepts.
She has been politically radical compared to the other X-Men the Genosha era, but that hasn’t been always apparent or mattered like in space or as a detective.