You guys really have missed the point of this historical moment, like Warren herself to a certain degree.
It seems clear to me Sen. Warren recognizes, like most lefties do, that Hillary will advance the progressive movement, not hinder it as you presume. Winning down-ballot elections is the most important step toward enacting progressive reforms, not electing a far-left president as you also mistakenly presume. Bernie has proven himself much too divisive (your piece itself is testament to his divisive influence) to effectively lead anything beyond a sing-a-long, let alone build a diverse coalition needed to push major legislation through Congress. The progressive movement has endured despite meager support from Bernie up until now, it certainly won’t be relying on him to continue on into the future.