Vaguely she felt that deceiving this woman would be very different to deceiving Whittington.
She intuitively felt that deceiving this woman would be different than deceiving Whittington because this woman was obviously a good person. 
mnli hypothesis: She intuitively felt that deceiving this woman would be different than deceiving Whittington because this woman was obviously a good person.  premise: Vaguely she felt that deceiving this woman would be very different to deceiving Whittington.