Malcolm in the Middle (2000)

S5E13 Lois's Sister

Lois' sister, Susan, comes to visit the family, showering Malcolm and Reese with lavish gifts while throwing sharp jabs at Lois and ignoring Hal, who she still resents for choosing Lois over her. The rivalry between the sisters escalates when Susan gifts Malcolm and Reese her prized '65 Mustang convertible. However, when Lois learns that Susan requires a kidney transplant, she decides to set aside her resentment and offers to donate one of her kidneys. Susan, however, views this act as just another chance for Lois to outshine her.