I believe her. I also believe she didn't want this leaked.
When did the dinner happen, 2018? 2 years ago (more like 1 and so-months, days, hours, you get the point).
Did Bernie apologize afterwards? Did they put differences aside? I do think people are making a mountain outta a molehill here. One could say, "But Bernie denied it!" and I could say, "Well, he's old. Maybe he forgot it. Maybe it wasn't a conversation that worthwhile to him." Warren, herself, seems like she'd hoped that bit never got out. For all we know, the time between then and now, the two forged a greater friendship and understanding of what they are running for since then.
This isn't Biden pretending he didn't vote for the Iraq War when he was a BIG guy stanning for it, or Buttigeig shittin' over the black folk of South Bend or Harris horrible stances on crime (especially that within Black communities). This was a private conversation at dinner 2 years ago where Bernie said something stupid and Warren disagreed and that was the end of it (until someone dug up that grave). Hell, it wasn't even "handsy" Biden and his touchy-feely Roman hands and Russian fingers.
Whether you are for Warren or Bernie, this leak benefits neither. Moderate, Republican-Lites like Buttigeig and Biden are sitting and laughing it up.