Certainly the fact the Ms. Stewart was formerly licensed, and had a successful career, as a stockbroker should not be left out of the mix. In her efforts to obtain her Series Seven (General Securites)License she was undoubtedly apprised of the vagaries of "insider trading" and then tested on the scope and depth of her knowledge in that area before she was allowed to enter the brokerage profession.
Much, much more than most others, Stewart had reason to know what she was doing might run her afoul of SEC rules and regs.
I agree. She hardly was a babe in the woods. Further, this wasn't just a friendly phone call. Waksal was the head of the company, one of the few who knew the stock was about to tank, and he tipped her off - a choice bit of info I'm sure the rest of his investors would like to have had.