I think she impressed Trump too. Trump seemed to actually look forward to her hard, pointed questions. He also seemed to enjoy that for once, Biden was getting similarly hard questions. Her questions to Biden kept him from going on another "Trump is bad, that's why you should vote for me." rant and actually have to present concrete plans. On some topics Biden did OK and on others he didn't do well.
Biden's attack style on Trump's COVID handling fell apart like in the VP debate when the moderator asked him what he would have done and what was his plan for the future. It is difficult to keep your credibility when you are harshly criticizing Trump's handling and then your plan seems identical.