Given the differences in their fitness levels, it's likely that Cassie will find the one-mile walk relatively easy and routine, while Sarah may find it more challenging since she has never worked out before. As they walk together, Cassie might set a moderate pace that is comfortable for her, but it could potentially be too fast for Sarah, causing her to feel fatigued or out of breath.
If they maintain a conversational pace, Sarah might be able to keep up with Cassie, but she may need to take breaks more frequently. Cassie's ability to sustain the activity without much strain may also encourage Sarah to push herself a bit more than usual, which could be a positive motivating factor. Overall, it could be an opportunity for both of them—Cassie can enjoy the walk and support Sarah, while Sarah can start exploring physical activity in a manageable way.