It's in a WaPo article from 2002, which I can't post anything from, of course. I've got the link if you want it, but I won't put it here. But the article states that the oldest son began to hate her when his child was born 2 years prior to that article in 2002. And he himself would not make any comments on it when he was asked.
Forgetting for a moment who she is and how much money she has, the fact that her eldest son has chosen to turn away from her means she is also deprived of contact with her only grandchild. Your source states the hatred began when the grandchild was born?
Let me guess. I'm an aussie. We are known to bet on anything. I'll wager Mrs Heinz-Kerry didn't approve of her son's choice of a wife. Who is she?
And then, to top it off, she marries a fool.
End result; very unhappy lady. Depression. And every day she must be asking herself, how do I get out of this?