Actually a majority of the "high elves" who were associated with the old Kirin Tor are more than likely Blood Elves (assuming they're still alive), so their relationship with the Horde goes back as far as the humans.
Since we've debunked the "stolen item" theory, we can move on. Wrathgate was an attack committed by a splinter rebel faction (controlled by the Legion) within the Forsaken. Blaming the Horde for their actions would be like blaming the Alliance for the actions of the Defias, the Southsea Pirates, etc. Furthermore, while Jaina was pissed off, it is likely she overcame that with the help of Kalecgos (thus the sound file). The Kirin Tor, a previously neutral faction, would not allow her to become their leader if she was "RAWR SMASH HORDE!" all the time. The Kirin Tor, as of yet, has no reason to join one side or the other, nor or they likely to do so. They, better than most, know that war between the Alliance and Horde is a bad thing, they're not going to go out of their way to facilitate without extreme belief that there is no other option.
As was pointed out, the tweet was vague. Was the "neutral? Pah!" referring to her, or her actions prior to assuming control.