She's an extremely easy target. Especially as Biden dying in office is not a mild possibility.
I honestly think that VP pick has hurt his chances, but that said I don't think he could have reasonably picked anyone else either. He was on a hiding to nothing with it.
The polls seemed to have levelled out at around an 8-9 point gap with Trump at his weakest conceivable position. I think Biden edges it still but Trump will surge back, especially if the US coronavirus spike levels out and miraculously there's no second wave - a V shaped recession would help Trump enormously.