The idea that people only tell the truth when they are drunk is laughable, and putting it in Latin (in vino veritas) doesn't make it any more true. When I'm drunk, I will say all sorts of things to get a reaction, and there doesn't have to be a reason for it. It's the main reason I never have more than one drink now.
Having said that, it sounds like your DIL doesn't really like you. The reason for that doesn't really matter because it's probably something you can't fix (a personality clash rather than something you can apologise for or stop doing/saying). She doesn't have to like you, but the two of you do need to work out a way to muddle along which doesn't affect your grandchildren. My mother hated her MIL and it was awful for me. My grandmother wasn't in any way perfect, but she loved me and was a far better grandparent to me than my mother was a parent. Please try to make sure that the children don't become aware of this, it will really hurt them.
I wouldn't normally suggest talking to your son about his wife, but in this case it might be better if he could mediate and you can agree on a way forward. It will probably mean limiting the time you have to spend with her, but it doesn't need to involve major drama. There might be one thing she dislikes doing (Sunday dinner, or visiting on set days, or whatever, in which case she could limit her attendance, or you could agree to not do a specific thing that annoys her. I don't know the specifics,obviously, but if a way can be found to make family relationships easier (and you promise to never throw this incident back in her face) then you can all benefit.
I know it's tempting to get stuck on wanting an apology, but this might well be a case of least said, soonest mended. The way forward does need to be talked about, probably through your son if she won't engage directly with you, but going over this won't help in the long term.