I think that there are also other times when Daisy treats Gatsby in a pretty despicable way.  I think maybe the most important example of this is what happens between them in Louisville.  I mean, she makes it clear that she really have feelings for him, but then she won't have him because he does not have enough money.  That seems despicable.

In a way, her interactions with him in the "present" are sort of despicable as well.  She leads him to think she'll love him again but then she goes back to Tom because she doesn't like how he got his money.

But I still think it's his own fault because he's the one who decided to keep trying to get this shallow woman...