Brother Issues
It is true that Karen was close to her brother and they indeed created magic whenever they performed together. However, there were many things that the two of them did not agree on. For one thing, Richard was reportedly a workaholic who did not give his sister a lot of freedom. He even had the final say on the schedule of their shows. It is easy to see why Karen wanted independence.
Walking To Her Death
Aside from dieting, Karen had a tendency to walk inordinate distances to aid her weight loss. The medical professional she was seeing asked her to stop and encouraged her family members to intervene. However, it was a little disastrous when the doctor rang up the other members of the Carpenter family.