Carrie was an intermediate druid. She only became recently, so she still had to cover up her own weaknesses with various items. For the team that she was leading, all the members were summoner druids. Of course, some of them were also learning how to cast elemental spells.
In Angstrom City, most young female elves strived to become like Carrie. They started by learning summoner druid spells (the most powerful ones to start with as a druid), then once they upgraded themselves to become a novice druid, they then had the option to select their specialized field.
Out of the many options that the female elves had, one of them was to become double-class druid like Carrie (both summoner and elemental). Many of them chose that since being in a double-class was a very common thing for the elves.
