Please do not take my post to be mean, I am new to this forum myself. I also have about 100 pounds to lose, and I know exactly how hard it is.
I am a registered nurse in a surgical ICU, and I work with people who have gastric surgery. For many, many of them, it does not work because they haven't fixed what's going on in their heads. You don't get to be 50, 100, 200 lbs overweight unless you frequently over-ride your body's satiety signals and eat for mental reasons. Your fiancee MUST improve her relationship with food in order to begin losing weight.
I have begun using the FitDay food log because it helps me to pinpoint my weaknesses, and the journal helps me to think about what's going on around me when I eat. I actually log on every time I am preparing a meal, so that I can enter my numbers before I get started and figure out what/how much I can eat for each meal before I blow my allowance for the day. It is a huuuuge eye opener to see how many calories you are consuming in a sitting. It also helps keep me in check, because if I have a chore (like entering intake into a food log) associated with eating, it helps to keep me from snacking when I'm not hungry.