A lot of you are ranking Katjaa lower then you should.
She has medical experience (Vet maybe but better than most)
She is very kind
She is realistic
She is one of the few level headed people in the group
She is focused on keeping morals and staying 'human'
I'd say aside from the medical experience, she was the much needed "Dale" character the group lacked in later episodes.
Good character with a lot of unseen potential taken out before she could shine.