I felt it was someting emotional. Like she got carried away during her monologue explaining why everything is unfair, to the point she got emotional and was about to tell something that Anduin, nobody in fact, is supposed to know. I'd guess a weakness, something she had hoped but which is finally impossible. We know that she is driven by emotions, most of her recent "feats" are. Teldrassil (I'm still not so sure about that, but for the community it is), her "The Horde is nothing",...
That's why I'm really afraid this was going to be about Nathanos and the fact his "body" is now dead and can't be revived so she won't have her happily ever after
That'd be vomiting rofl.