Simone (as I remember) was simply obsessed with power and wanting more of it/taking her rightful place; she liked the idea of guns simply because 'more power', she thought slayers should be able to do what they want because 'slayer'.
Also I don't remember Simone ever showing guilt/doubt over then things she went on to do, even though she led many other slayers down that path.
Ultimately Faith hated herself and wanted somewhere to belong and a family; she simply made the wrong/'easy' choice about how to get it; the 'might makes right' aspect of slayer-ness was just shallow justification which fell apart in 'Who Are You?.
Even taking into account the chosen medium- comics- Simone was a poor antagonist.