I'm guessing her popularity has been waning. Make no mistake, if she was making the Food Network a huge sum of money then she would still be on the Food Network.
I'm guessing the same because her contract is up this month and if she was still a huge hit they would have her people talking about her ideas for new shows and episodes. Then the lawsuit happened and I feel the ratings were fine, but not amazing anymore and Food Network feels that the bad press would hurt her more where it wasn't worth it.
Jubba the Hut, I mean Rush Limfatass is still on the radio because he still makes money for the few old people that listen to his crap.