We met our favorite trampoline when she was determined to kill just to get herself whiter and flatter! Rose saw through her from the start!
"I had hoped to manufacture a hostage situation, with myself as one of the victims. The compensation would have been enormous. "
"Five billion years and it still comes down to money. "
"Do you think it's cheap looking like this? Flatness costs a fortune. "
Even upon our next meeting she has not changed at all. she steals Rose's body, tried to kill The Doctor and blackmail a hospital. She even plans to ditch Rose for something "less common".
"Over the years, I've thought of a thousand ways to kill you, Doctor. And now, that's exactly what I've got. One thousand diseases. They pump the patients with a top-up every ten minutes. You've got about... three minutes left. Enjoy."
After being inside of Rose's mind and helping to save an entire new race of people with The Doctor, she changes
"I'm dying. But that's fine."
"I can take you to the City."
"No, you won't. Everything's new on this planet. There's no place for Chip and me anymore. You're right, Doctor. It's time to die….And that's good."
"Excuse me... Lady Cassandra…"
"I'm sorry, I don't need anything right now. I'm fine, thank you."
"No - I just wanted to say... you look beautiful."
"Well. That's very kind, you strange little thing. Thank you very much."
"I mean it. You look... so beautiful."
"Thank you."
Personal note: All time best who moment for me, Cassandra in The Doctor