'Cause it isn't. 'Cause she isn't.
Big words don't make the style, mate. People with a very well developed writing style are less than your fingers and toes together. In the whole world.
She isn't great. Mind you she got the hang of writing books and I can't twist my soul and say she sucks. She doesn't. But she isn't anything amazing either.
See, I only recently discovered some good writers with a great style, one of them being Sir Terry Pratchett, though many would disagree.
And I'm damn afraid that most of your bestsellers, including Anne Rice do not have good styles. To be read by masses means you must scoop to an overall level and sacrifice Irony, Sarcasm and side stories. You really should try Pratchett once, you'd see what deep Irony means.
Developing a "great" writing style can't happen when you're writing a book that merely contains any hidden messages, and said likes of irony. You can't twist the twist it's self if you are satisfied with one bend in the curve.
And hollyuk, make sure your wife doesn't see this. We women are very skilled in using tenderizer hammers or other kitchen cutlery.