People (mostly women) who have their gallbladder removed often don't do well with eating fatty foods, that is true.
However, their gallbladder issue was not likely caused by eating too much fat. As Robb Wolf and I have noticed, gallbladders go bad in people with gluten intolerances quite often.
The key idea is that not having a gallbladder does not exempt one from the fact that the body still needs ESSENTIAL (key word there) fatty acids. Their inability to digest them well is the problem.
Supplemental ox bile will solve the problem. Honestly, I think removing someone's gallbladder and not recommending supplemental ox bile (or big doses of lipase) is tantamount to malpractice.
One thing you might tell her that could change her view. I consistently see patients who have had their gallbladder out (and don't supplement afterward) gain major amounts of weight after the surgery...and the timing never seems to be "coincidental".