In Like Water for Chocolate and in House of the Spirits, the idea of power is expressed in one way through the themes of victim and victimization, justice and injustice and the mutual themes of sex roles and love and passion. In the case of sex roles, power is limited by sex role for females and embedded in sex roles for males. For example, in Like Water for Chocolate, Tita is confined by her mother (a fully conquered victim of sex roles) to a strict sex role by restricting Tita to the kitchen where, through magical realism, Tita's desires and passions find their way into the food she prepares.
As another example, in House of the Spirits, Esteban comes into sex role related conflict with female characters from employees to peasant women thus emphasizing the conflict detailed between himself and his wife Clara whom he expects to fulfill only the sex role of mother and caretaker of the home. Clara goes beyond this though and teaches the peasant women about equality, but, when the ultimate clash comes with Esteban and Clara moves to the big house, Esteban's ultimate sex role power is shown because of Clara's eventual choice to die, which is surely a result of her experience with Esteban.
It could be argued (particulalry with The Houe of th Spirits) that power is portrayed as a patriarchal construct which women must of necessity (and successfully do, usually) subvert. If women cannot subvert this construct then power becomes corrupt and unprincipled (as with the coup near the end of the novel and the relation between Alba and her torturer after she is arrested).