Well, John gave her that AMEX card, so don't blame her. You never hear anyone complaining about about Olivia Harrison spending all of George's Beatles money, and she came around long after Yoko did.
No one understands Yoko's stupid caterwauling. Not even Yoko. It's pointless, and the world sure doesn't need it. But it has nothing to do with whether she contributed to one of Lennon's songs. He said that she did, so she's entitled to the credit.
Everything I read about how she and John got together, and how she asserted control over him once they did, makes my skin crawl. But that was John's choice to make. He was a big boy - a big, rich, famous boy - so he could have done whatever he wanted to do, and he chose to be JohnandYoko (and told people to write it that way).
Much of Yoko's art and all of her music is dumb, but so what? Most art and music is dumb. But I have to say that any hatred for Yoko that stems from The Beatles or John Lennon is also dumb. She attached herself to Lennon, and we may not like that, but he seemed to like it, so what can you say about that? They both got what they wanted and needed, which is pretty much the definition of a perfect relationship between two people.