I have never been to a show (of any kind) where they check a horses papers. Your friend may have meant that certain bloodlines tend to perform or place better than other bloodlines. That is pretty standard for most breeds (the "trendy" blood line of the moment) this is usually based on how animals from that bloodline look or carry themselves.
Your mare has Collectors Go Boy as both a sire and Grandsire - I am not sure if that is to her advantage or a disadvantage. The picture on all breed is not flattering to your mare - I realize she is young and has some years for filling out and growing to do.
Her success in the show ring will really depend on what kind of show you want to do and her training.
We have 3 TWH and love them all.