If you like the rabbit at Cookstown, then you should arrange to visit the breeder.
Like I said, all rabbits are individual. Girls are not worse than boys, boys aren't worse than girls.
What that person is likely referring to is an unspayed (female), or un-neutered (male) rabbit.
A rabbit that doesn't get spayed or neutered, tends to be more territorial. They may spray urine, hump people/things, and may defend their territory (possibly by nipping with the teeth).
A rabbit that is spayed or neutered will be far calmer.
I would suggest to you that the person who said girls were mean, was probably someone who did not choose to spay their bunny. She may have been feeling scared, or territorial, or simply hormonal.
Spay/Neuter usually starts at $100-200, and may increase in price from there.
Most people spay/neuter around 8 months of age. That way, the rabbit has had the benefit of hormones to grow, but isn't yet in the habit of spraying, etc.
(Think of them as crazy teenagers).
However, any rabbit can be spayed/neutered at virtually any age.
The result is (usually) a calmer, happier rabbit.