From what I've heard, she is disliked because
1) she has this "country girl", simple and unfussy personna on her blog, but she actually comes from a wealthy family (her father is a doctor, and she has tales of going to the country club), and her husband's family are very wealthy as well. THere is of course nothing wrong with that ! But it's tough to buy the "keeping it real " because her financial situation (even before the cookbooks) is very different from other farming or ranching families.
2) she rarely quotes the source of her recipes, which may lead people to believe she invented them. A lot of the recipes she uses have been around for decades, yet she does not mention that . She sometimes mentions using her grandmother's recipes, or her friend's , but she does not have a source for most of her recipes.
3) Most of her recipes are very VERY high in fat, low in fiber, and use very little vegetables.
I don't have an opinion personally, I like some of her recipes, I dislike some of them. I've never watched her show. I used to follow her , but I've stopped reading her blog after the sour cream enchiladas recipes because her recipes are simply too caloric for my family.