The app of course needs access to the Internet, through your WiFi or mobile Internet. However, depending on the app, phone OS and the security configuration of your local network setup it could have access to other devices as well.

But that's usually on purpose or by accident of the user. In court, one valid question could be if TikTok tries to make use of such a configuration, and for what reasons.

So I think the question itself is not that bad, if it got a clarification / follow-up question like the above.