I think the target/treat training may come in useful here. As nonsense is quite treat motivated, you should be able to continue with what you are currently doing- getting her to come closer to you to get a treat. Slowly, you may be able to morph this into stepping on your arm for the treat. If you put your arm at the edge of the cage top and get her to come across the cage to you for a treat, you may be able to continue this into her actually stepping on to your arm to get at the treat by holding the treat out of reach of the cage top- so that her only option to get the treat is to step on your arm to get it. Remember, patience is key. You may need to wait before moving on to this step until she is comfortable approaching you/your arm.
I am envious that nonsense is doing well with the target/treat training. I can offer Alfie his favourite foods as a reward as much as I like, if he doesn't want to do what I'm asking, he's not interested! And target training? No chance- he tries to kill whatever I used as a target!! Haha.
The hardest part is absorbing a bite. If she does happen to bite, you're best off trying your hardest not to react (easier said than done, I know!). If you can absorb the bite without reacting (other than to end the session and give her some space) then it isn't so much of a game to her anymore. Alfie still nips me from time to time. When this happens he is either moved to his cage/a perch away from me- or if he's already on his cage/a perch then I just move away and give him a little time and space to get over whatever he's grumpy about.