What is good evidence for Atheism?

I'm an Atheist in an argument with this girl on Youtube who says I need evidence for my Atheism. I told her I didn't because that's like saying I need a reason for why I don't believe in Santa Claus and she said I do need reasons for not believing in Santa Claus and then she gave me all these logical reasons for why she doesn't believe in Santa Claus. Help!