See my answer to this question: http://paleohacks.com/questions/126030/digestive-enzyme-brands/132913#132913
Without a gallbladder, she'll need digestive enzymes to help process the fats properly. Going low fat is not a good idea. Also, using coconut oil where possible will help because about half of it is MCT oil, it won't require bile to process and has wonderful positive effects on the body.
The initial few months after the surgery will be hard because there's a lot of adjustment. The way this thing works is that they remove the gall bladder and connect the bile directly to the stomach, so there's a constant drip of bile.
If she for some reason doesn't have an appetite, she may experience bile reflux and throw up bile (will be very bitter and look bright yellow). But apparently there's a link to this operation and colon cancer because all of this bile goes downstream and since it has nothing to process, it may attack the lining of the intestines. So avoid fats is not a good idea.
Eating some fat throughout the day is a better thing to do, but in small amounts, so it's spread out.
Supposedly, over time, the bile duct becomes a rudimentary gall bladder, but it won't have the same capability as before.