Yes, nutritionists are just like personal trainers--some are complete shit and others rule. Yes, the only way to get progress is to measure progress. You are the trainer, she's the client. It sucks when you can't tie it all together with nutrition, but sometimes that is what you have to work with. I am cureently in the same boat with a novice competition prep. Only I am doing her nutrition and somebody else her training.
You need to meaure her progress. Off the top of my head though, she is cheating if she is not losing weight and assuming there are no hormonal issues. It IS possible that you undereat and dont lose weight, this happened with another client I had, who had to actually increase her calories. But this is extremely rare in an obese person--emotional issues, constant "uncounted" snacking, lack of food journalling EVERY SINGLE THING she puts in her mouth, these are all much bigger issues.
And let me reiterate--YOU are the trainer, YOU are in charge and you should make sure you know what is going on in measurements. This is science 101...you need a baseline to predict and assess changes from. Without that, youwon't know what or how to change. Weighing every day is not good for most people's mental edge--they get fixated and frustrated, but weigh at least 2x a month.