Try starting out in a room with a window where she has very few hiding places. Set up a branch or shelf by a window as high as you can reach and let her sit up there for a while. You could also set a chair by the window and sit with her on your arm for a while as she looks out the window. Handling her every day around the same time is also good. Daily repetition will get her used to being handled and eventually look forward to that time of day to being able to look at the natural world.

I always thought of it kind of like an old man that likes to watch the ducks at the nursing home. He might be grumpy most of the day, but looks forward to looking out the window at the ducks at a certain time of the day. It gives him something to do at that certain time of day that he enjoys and makes him more enjoyable to be around.

Remember, iguanas are arboreal creatures. If Bella has some trees, birds and other wildlife to look out at and feel like she is high up in a tree while doing so she will look forward to that moment and be easier to handle.