Bertha

Bertha is the second Elite Four member in Diamond/Pearl and Platinum. Her team is comprised of -type Pokemon. With this said, it is best to avoid using type Pokemon against her, as they will not last long in the battle. The best alternative is to have either a Water or most recommended Grass type Pokemon because she has part-water type Pokemon, such as Empoleon or Torterra, when fighting her. The strongest Pokemon on her team is Hippowdon. Her Pokemon levels range in the 50's, so it is wise to be prepared with Potions, Revives, etc., and leveled up properly. In Platinum, her Pokemon will get stronger the more you battle her.