Bob has decided to get married

Bob has decided to get married, but before making his request he wants to talk to his mother ...
- You know Mom, I met a beautiful girl, I would like to marry her but I would still like you to meet her before.
- Yes, if you want my son, said the mother.
- That's what we'll do, Bob answers, next Saturday, I'll come with three girlfriends. One of her is the woman I love. I do not tell you which one and we talk about it afterwards, okay?
"Yes, if you want my son," said the mother. Saturday comes, Bob comes with his three girlfriends all beautiful, smart etc. The dinner is going on, the girls are leaving.
- So Mom, said Bob, do you think you've found out who's the woman of my life?
And the mother answers ...
- It would not be the one who had the blue dress?
Bob stunned ...
- That's her. But how did you do it? They are all three beautiful, nice, etc ... How did you do to identify it right away?
And the mother answers ...
- I do not know ... I do not like it!
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