Meeting Tsul'reksh was probably the best thing to happen to tyranny thus far in her journey in regards to truly setting up her arc. Her and her sisters were created with the specific purpose to serve the creed, and, we can assume she's had no other interacts with demons apart from them. The sisters have more human names. They're still obviously demons, but they also have more appealing/palatable bodies. They were brought into this environment that is forcing them into a specific mold, and yeah, Tyranny might be aware that the creed is bullshit (she was in on it after all) but she still subscribes to their belief that demons are inherently corrupt creatures with no chance of being "saved". She was never given the chance to understand what she truly is outside of the propaganda that's surrounded her from day one.

you’re serving face? the vampire lestat just told you to off yourself and you’re serving face? that’s the vampire armand right there

"Whadda they gonna do, kill me twice?"

"Fucking good people bullshit. Fine. You rolled a 19."

Ah yes King Augustus Valian