Let's face it.
You want to enslave Cassandra.
I mean, who wouldn't?
But just flatout enslaving her is boring.
Let's have her beg to become your willing slave.
As for how it happens, well...
That's what this transcript is here for.
It starts once you meet her in the Hallway and ends once she becomes your willing slave.
Though, if you're curious how you ended up here, you might want to check the Intro Transcript.