Your budgie is till quite young and it is sort of like a scary new world outside of her cage. Her cage is her safety and comfort.
Does she step up for you easily? If so hold some millet and get her to step up onto your finger then slowly move your hand out of the cage. I have a perch on the outside of the cage near the door for my birds they love sitting there and using it as a hop before they go back in perch.
Also get a small bird gym or make one place this on top of the cage and place her there. She will learn with time that it is safe outside as well as in her cage.