This is a very hard question to answer because you are correct, there is conflicting information out there and GI issues, symptoms and the bodies response to intervention can be varied from person to person. It depends on what her previous diet was like, gut flora, recovery time, etc can all impact interventions. Is there a dietitian that you can work with associated with the facility where the surgery will be performed? It would be best to have a dietitian that can work with your daughter, monitor interventions and make changes based on what she is experiencing. It is very hard to give general advice for a specific condition.
The most important step to take is to advance slowly and monitor what is tolerated. The body usually does a good job of letting you know what it can and cannot tolerate. I would start with small portions and lower fiber foods, working your way up to things with a little more fiber content. Again monitoring what is tolerated will be your best indicator of how to advance through the diet.