While DNC chairs have consolidated a great deal of power, have many ways to self-deal and dig-in using the bylaws (such as determining caucus partitions/schedules and being superdelegates for life) their position is subject to internal approval of DNC membership itself. That is, you can just fire them. You don’t have to wait for them to resign to call for their replacement.
Regardless the committee is more like an HOA than a government body. They make suggestions and endorsements, host the convention, support candidacies strategically and financially, and threaten to take that away if you break rank. But they have no authority to say who runs, or even who runs as a Democrat.
But most importantly, AOC has always been a grass roots candidate. It would be great to have DNC support, their backing and resources, but she’s never needed it before. I can’t imagine she wants it now.
In fact, I think it’s far more likely that the DNC will one day ask her to endorse them.