I have not tried her pants, but I have purchased 6 of her tops in a size medium. They fit fine and wash well. Of the QVC brands I purchase Denim & Co, Susan Graver and Issac Mizrahi I wear a medium in all of them. I have also purchased a couple Joan Rivers and Bob Mackie tops also in a medium. So I would say the sizing of tops is consistent with most of the other brands at QVC.
As for pants, In D&C I buy Petite Medium, Susan Graver Petite 12 or Petite Medium and Issac Petite 14. I just ordered my first pair of C Wonder Ankle Pants ( I have them on now) and I ordered a Petite 14. I was undecided between the 12 and 14 and glad I went to the 14. Don't know if this helps you with the pants sizing or not. Seems to be some difference between brands I buy. In the brick and mortar stores, I wear a Petite 12.