AOC is not part of the dominant faction of the Democratic Party; both major US parties are basically broad coalition, the Republicans basically Right to Far Right (with he latter being currently dominant) while the Democrats are basically Center-Right (dominant) to Center Left. (The “Democratic Socialists” within and aligned with the Democratic Party are more Social Democrats by any non-US standard than actual Socialists.)

There is effectively no real representation of the left, beyond the center-left, in US electoral politics.