It refutes the claim "that's the mirror"
because the person in the mirror would have tits, because she has tits.

The argument runs thus:
1. observation: person looks at me who possesses property "sour-faced"
2. hypothesis: person is my reflection
3. observation: I have tits, but person has no tits
4. therefore: person is not my reflection
( Moon Girl Technologies horrendous beanbag, Thu 4 Jun 2009, 18:01, archived)