I read in an interview with the director that he considers the food fight scene a sex scene. I don't see it. I watched the scene a few times, and I still don't see it. But what do I know, I think Catcher in the Rye is a dumb book.
shareFood scenes (whether fighting or consuming) are often used to stand in for sex scenes in film and books because of the intimate experience/ritual of preparing things.
In this case, the women are acting against traditional versions of making food, just as in their intimate relationships they are going against what is "supposed" to happen (a man and a woman).
In the novel the two women do have sex, but for the movie they downplayed their romantic relationship.
The food fight scene nods to their deeper relationship without being explicit. It's a scene that can be argued both ways--it could be a metaphoric depiction of sex or it could just be two women throwing flour at each other.