Karen joined Holby A&E at the beginning of series 8. She managed to get on everyone's nerves in the beginning; although her relationships with the rest of the staff improved, she treated the paramedics as if they were merely ambulance drivers. Her attitude towards them didn't help when she was caught up in an accident and the ambulance took hours to arrive.
Karen was a good doctor but her attitude caused some problems. She gradually became more aware of other people's feelings, and got on OK with most people by the time she left. Mike Barratt ordered her to take study leave partway through the series after she was becoming exhausted trying to swot for exams as well as working.