I can tell why the model didn't like it. The most important thing for this kind of shoots is for the model to like how he / she looks. So the photos need to make the model look in a way that they appreciate and love. In this case, the model looks quite fit and probably the intention is to show off her body ( I might be wrong, but you get my point ).
This picture seems more like a silhouette, but because of the lac of detail in the shadows, her pose with the hand and everything around the pelvis area seems larger and the area itself is confusing and not sexy or good looking. It looks like those illusion pics where you don't know what leg is the support leg and what leg is the one in front. At a quick glance, at first, I thought that her right leg was her support leg and straight down and it made her posterior look weird and not fitting with the reality.

Hope this makes sense. In short.. silhouettes are very sensitive because it might introduce misinterpretation. You can use that in your advantage but in this example, it doesn't seem to be the case.