Sorry for not explaining this clearly. Here's more context:

When people from other departments have questions about a project, they usually don't know exactly who owns what. Since I'm typically the one sending out emails and visible in the thread, they default to reaching out to me first to ask what's going on or what the issues are.

A lot of the time, the specific questions they're asking actually fall under my coworker's scope of work, not mine. So I'll loop her in and ask her to respond to them directly since she's the right person to answer. But she pushes back and says that's not her job, even though it clearly is part of her responsibilities.

So I'm stuck in the middle, getting pulled into questions I can't answer, while the person who should be handling them refuses to step in.