Like Water for Chocolate, or "Como Agua Para Chocolate," can be taken two different ways.
The first, and more innocent, of the two is the common Mexican
expression to indicate anger. We're not surprised that much of Tita's
anger comes from Pouty Pedro:
[…] it seemed [Pedro's] rage dominated the thoughts and actions of everyone in the house. Tita was literally "like water for chocolate"—she was on the verge of boiling over. (8,513)
The second meaning can be understood in a more risqué manner. In Mexico, hot chocolate is prepared with water (not milk). When the water is hot enough (near boiling) it's ready to receive the chocolate. All that heat and almost bubbling action describes a state of arousal or passion, like that between Pedro and Tita, Juan and Gertrudis, and, yes, even Mama Elena and her ill-fated lover, Jose.