Y’all need to chill
If Bonney can become Nika, that’s because SHES 12. The mind of a child that doesn’t understand limits, that is told that Nika is a god of freedom and can move his body however she sees fit. And then she sees that Luffy has been given that ability as well. She doesn’t know about his fruit, she doesn’t know about the limitations. She just knows “this man feels truly free and looks just like the god my daddy thought me about.” Which would beg the question of any 12 year old who doesn’t know there own limits, “Why can’t I do the same?”
As Saturn said, her power is based on how strongly she believes in the possibility of these futures. And her faith in this future is at its peak right now.
Is Nika lame, sure. But Bonney using this power is far from the bad part of this chapter so far.