Problem is that Alleria majorly hates Orcs and Trolls.

"Though they were successful in repelling the Horde invasion, it came at a terrible cost: eighteen of her kin, including her younger brother, Lirath, were killed. Devastated, Alleria sought comfort in the arms of Turalyon, but ultimately, she chose to dedicate herself to revenge.
Alleria in Warcraft II
Alleria in Warcraft II
Alleria in Warcraft II manual.
Alleria in Warcraft II manual.

To the horror of her friends, Alleria came to see the orcs as little more than vermin to be exterminated.BtDP #? Alleria hunted down the Bleeding Hollow Clan whom had so far escaped capture. When the orcs rallied behind Ner'zhul and the death knights, Alleria agreed to lead her rangers beyond the Dark Portal into Draenor to take to gain vengeance for Quel'Thalas and stop the Horde once and for all. Before she left, she had her necklace melted down into three pieces.BtDP 198 She kept the emerald for herself and sent the ruby to Vereesa and the sapphire to Sylvanas, using Verana, her lieutenant, as the emissary. "

From http://www.wowwiki.com/Alleria