She can still refuse the call! But "Okay, let's run to the Millennium Falcon, return this robot to the resistance so I can go back home!!" would be SO much more character-driven than getting swept up in everybody else's story. It just kinda fumbles and feels aimless and like a series of events until about the time she picks up the lightsaber.
Which is basically the inciting incident to the break into act 3, because then she runs into the forest (a choice) and *chooses* to try and shoot Kylo.