I think you're doing the right thing, strudel. If you insisted she step up every time, she'd only become resentful and it could be the beginning of bad behaviours. If she's happy just sitting, then let her just sit. Of course, you could always try luring her onto your hand with a food treat. That way, it's a win-win.
I read somewhere recently about a person who taught their bird to forage. First, they worked out what the favoured food treat was (by watching which items the bird always chose from a mixture). Then, they would put that item into a paper cup so the bird could see it. When the bird had taken the treat a few times, then, they folded the paper cup so that you couldn't see the treat, but the bird knew it was there and got it out. After that, it was step by step, hiding the treat more and more until it was firmly encased inside folded paper cups and the only way for the bird to get it was by ripping and tearing the cups open.
Dominic likes egg carton material very much. Maybe you could try cutting sections of egg carton and placing your food treat in one of those. Then, you could squash the little egg-cup thingo more and more until the treat is hidden (letting the bird search for and find it at each step, of course). Eventually, you could put the treat in an egg-cup thingo and then squash a second egg-cup thingo on top of it so your bird really has to chew and rip to get the treat out.
Or, you could try the above system using paper or light cardboard (cereal boxes?) All my birds respond wildly to any object that clearly has 'something' inside it. Something about the rattling makes them curious. Maybe you could put a peanut or almond inside a paper cylinder and fold the ends shut. See if your bird will chomp the paper apart to get the treat.
Anyway, I thought the idea of teaching a bird step by step how to get into stuff was a really good one. Hand-raised birds especially don't learn a lot of stuff that their parents would have taught them. In the same way, my Dom has learned to forage by watching the Beaks do it. Now,
that was handy!

Saved me a lot of trial and error!
Best of luck with your Galah. I hope you can get her chewing and chomping - there's so much satisfaction to be had from it and I'm sure she'd be happier once she learns.