My worry about AOC as candidate is that she’s relatively alone in her political space, and is far from having Bernie’s weight as of today. She’s in the Democratic party, sure, but she’s in a very small faction inside of it, which may lead to a Corbyn situation: she takes the helm of the party, but centrist figures begin attacking her from her own ranks with the support of the media until she’s forced to concede to a moderate.
On the other hand, if you manage to get 100, 200 elected representatives in the Democratic party who are clearly ideologically aligned with AOC, making her the nominee is no longer a battle, but rather, it becomes the natural consequence of the balance of power within the party.