Like I told you, the narrative build up is there
Saturn is the reason for why everything this arc is happening
Ginny's death, Kuma being a robot, Kizaru's conflicted status, Vegapunk's death, Gorosei summoning, and the list is long
There are exceptions. Jack is the reason everything is happening in Zou, yet he isn't taken out there.
But rather than generalising, lets take the main analogue for Bonney: Robin. Both were young girls who lost their family due to void century connections, both had their parents abandon them for their safety, both spent their childhood on the run, and both in the climactic moment of the arc decide they want to die before their loved ones give them a reason to live.
Unlike other damsels, Robin does not need Luffy to defeat a single big bad for her. Her problems are much more complicated than that. The victory is that Luffy gives her hope, and because of that she can put her past into a new light for a future payoff when she sets it all right.
Bonney is the same. She has one of the most powerful devil fruits in the verse, and Luffy by restoring her faith has just supercharged it. In addition, she commands Kuma and every single pacifista on the planet. She does not need Luffy to save her because he already has. Her father already has. She doesn't need to pursue her vendetta anymore. Now she's going to go on a journey to restore her father's consciousness and discover more about Nika, and if Saturn is going to go down for good, it will be once that arc of hers reaches its conclusion, by which point Saturn will have no power over her and Kuma anymore.