What is true that Representatives are, in majority, not millionaires.
They are in the Senate! Almost entirely, with some even approaching billionaire status. But in the Representatives, while some have accrued a great deal of wealth, the majority of them cannot maintain two residences - one in their home district and one in DC - on a Congressional salary alone. So, yes, lobbyists can use that to make their offers mighty tempting to people who want to serve in Congress but find their salary package inadequate for how that works.
Having said that, you might have some ideas about how to solve that situation that differs from Ocasio-Cortez's proposals - and, fine, I'm not going to argue that. But that doesn't mean that part of what she's saying isn't true.