She broke free from a tyrant and went on to occupy quite a nice bit of land... with her own city underneath, which I often visit for the Auction Houses. She wishes to give her kind the power of reproduction through the Val'kyr. Sylvanas is committed to the survival of her race, like all Sin'dorei I know, and that is why I approve of her induction as Warchief.
And because... remember that Scourge officer I mentioned? I served the Scourge for a time. As an enchantress for their plate wearing warriors, carving terrible curses into their armors to terrify and harm their enemies. And as a tailor for sewing together new robes for their casters. It was tireless work because they did not actually kill me like most. They felt that true...