To be honest Alleria and a lot of Void Elf NPC's come across as pretty suspect in general, i recall 2 members of the Void Elf Expidition team talk about feeding souls to the void and listening to the whispers, and a few other Void Elf npcs say similar things to horde players. Alleria's apparent desire to take Quel'thalas for the Alliance is also put in a darker light with how the Void wanted corrupt the Sunwell.
Not saying i want them to pull a corruption/madness thing with Alleria, but they seem to be implying such a direction with various comments and interactions by void elf npc's, especially since the Void Lords seem like a looming threat now that the Old Gods are dealt with.