More or less, yes. In theory, it makes sense that she didn't mind working with him until he started going on about how he would force everyone to serve him because her whole backstory is that she was murdered and her spirit was enslaved by Arthas, the man who would later become the Lich King(that's the voice you hear in the cinematic). The issue is that this just makes her an absolute moron.
The Jailer is WoW's version of the devil who rules over the Maw, WoW's version of hell. The Lich King she hates so much? The Jailer supplied the weapons and armor that created him. The white-haired dude with the sword? He's the pure-hearted human king. Sylvanas helped the Jailer strip away his free will and turn him into a mindless servant which, btw, makes him look nearly identical to Arthas.
But the most galling thing is that Sylvanas was seemingly doing all of this for altruistic reasons because she believed WoW-Satan was going to change things for the better. What pisses people off about this is that Sylvanas did a genocide. That's not exaggeration. She knew only innocent non-combatants were left in the night elf home and she burned it to the ground. And if that's not bad enough, part of her work for the Jailer was breaking the "engine of death." So every single person that died there went straight to the Maw to be tortured for all eternity.
Geez. Shes basically a WoW hitler then. No way can you redeem that shit.