The thing about Cassandra is that she seems so vain. All of the ridiculous lengths she goes to for the sake of beauty. But it isn’t until this scene that you understand, because it seems like she’s meeting herself for the sake of more vanity. But then she repeats to her younger self that she is beautiful and you see the look on her face change and that’s when you see, because you can tell from the flippant way she regards it the first time that people had been telling her she was beautiful her whole life, but when this strange person comes up to her and tells her with such heartfelt sincerity that she is beautiful, this was the only time which Cassandra believed it. The only time she actually felt beautiful.
Doctor Who Series 2: New Earth