She is very conscious about the environment and had taken part in protests with her mother, leading her to be known as "tree hugger", or "hippy". She is very outgoing and energetic but becomes a bit more subdued as the seriousness of the situation dawns on her.
She is changed in personality in the third series, being rather solemn. She is the first member of the group to experience alien contact. She begins to like David, but later finds him frustrating and they fall out for a while. At first she constantly has arguments with Chrissie but the two learn to get along, mainly because Chrissie becomes less awkward. She, like David, survives because she was sent back to Falkirk before the rest of the group and did not catch the red eye virus. David and Sarah forgive each other and become much closer after their experiences together.