The Sentinels were there to deliver sickening news: Sentinels who had been assigned to guard a convoy of supplies were brutally murdered -- not just murdered, but outright slaughtered. The skins of the Sentinels were found hanging from the trees, the rest of the bodies having been chopped up and left for the carrion birds. On the skins, painted in the Sentinels' own blood, was the symbol of the Horde.
Jaina was taken aback, convinced that there was no way that this could have been authorized by Thrall, but Varian was quick to place the blame firmly on the Warchief. When Jaina attempted to remind him that Thrall was no more responsible for all the Orcs than Varian was responsible for the Defias, Varian snapped. Though Varian's odd ordeal of being split into two physical bodies had ended, he was still very much two men in one body -- the wise ruler Varian, and the bloodthirsty and rash warrior Lo'Gosh. It was Lo'Gosh who then taunted Jaina about her poor decisions with Arthas, needling her to the core -- and it was Varian's son Anduin who happened to walk in at that precise moment.
But she wasn't home on pleasure. Instead, she had scheduled a meeting with Thrall to discuss the incident in Ashenvale. Varian had sent a courier to Thrall, demanding that he apologize for the actions of his people and turn over those responsible for the slaughter. While Thrall was happy enough to see Jaina, to her dismay, he replied that while he would return a note stating his disapproval of the incident, he would not be offering an apology. Nor would he be turning over the criminals.
*Admin Note* See, this is what happens if you eat lead paint chips as a child. Spammers...when will they ever learn? Post edited to remove links.