Well I have always thought of PA as behavior that makes another feel bad but is so sneaky that you can't really call them on it, at the time. They have covered their ass while still hurting others feelings. So while you COULD have called her on the "tired" talk during dinner or yawning or just plain appearing uninterested, she would have responded "I am just tired!! I'm not trying to hurt anyone's feelings! Why is it all about you?!"
My MIL is passive aggressive and, boy, is she hard to deal with sometimes. She will make plans with me and then "forget" about them..I have to call and remind her of them, etc. I guess it gives the person a feeling of power, I don't know. I really know very little about it, actually. I'm sure others here could give you better information.
But I do agree that your wife appeared to be projecting herself onto you. Or.....maybe you are both PA and both acting out this silent war against the other...?
I don't know, Dog, all I know is that a husband deserves a better birthday from his wife than what she coughed up. It was a piss poor effort and I hope she makes it up to you soon.