I'm so sorry about your bad experience. Elizabeth Taylor promoted a scent called White Diamonds. Maybe your seller was trading on that. What a weasel!
Diamonds are diamonds. Colored ("fancy") stones are rare and very expensive. The Federal Trade Commission has rules about selling gemstones, and they have a pamphlet you can download on their website.
There are white topaz (love those!), white zircon (NOT CZ), and white sapphire. These are all beautiful stones, and I have some in my personal collection.
There is a diamond simulant at jtv.com called Bella Luce, and another available there and elsewhere called Moissanite. These are really beautiful, and they are available as loose stones and in jewelry.
Diamonds may be a girl's best friend, but that stone is controlled by a monopoly. Go for beauty, but don't get suckered.