A lot of people use the vulnerability of birds being low to "teach" them to step up. Well, the bird only steps up from down low, it doesn't teach them to step up from anywhere else. If they are lucky, the bird may learn to step up from other locations.
The reward when she's up high may not be a high enough reward for her to move. Teach her to come to you at a location where she will succeed. Reward, reward, reward! Be sure to practice this behavior in a variety of locations and at slightly different heights. As she becomes reliable with the behavior, you can then try at lower and higher heights.
The reward can be anything from food, treats, scritches, verbal praise, a toy.... anything the bird is willing to work for.
What you need to do is to generalize the behavior. You might say that what a bird learns in "school" stays in "school", unless you generalize that behavior everywhere that you can. The more generalized that behavior comes, the more the bird is willing to do that behavior, even in strange, new places.
If you can, for now, try to avoid letting her get higher than you until she has learned to generalize. If she does, you may need to try some higher reward treats, toys or whatever. Worse case, you may need to get higher, but it doesn't help if you always have to be higher than her to get her to step up. You want her to learn to come down.
