My supervisor is making me work on something that is not my PhD project. What should I do?
And during all our meetings so far, we haven’t really discussed my topic, the chapters of my thesis, my research questions, the literature I should be looking at, or the instruments I need for answering my research questions


So, that seems to suggest a natural course of action.  Let her know that at your next meeting, you want to focus on making concrete plans about your thesis.  Then do it.  Come with a list of questions and make notes.  Be sure to bring up the topic of how the big study will tie in to your thesis work, and how she expects you to balance the time spent on both of them.

It sounds like maybe you've been pretty passive so far in your interactions with her.  Clearly it's not working, so time to try being more assertive.

If she won't have that discussion, or won't stay on topic, then you probably ought to start looking for a new supervisor.