East of Eden question

Never read EofE myself, but I've seen the movie. Years ago, my MIL and I were watching it on AMC. James Dean and Julie Harris are talking outside, in a field/meadow/whatever. Another young woman walks up, doesn't engage them, but plunks down a few feet away and keeps looking over her shoulder at JD. JH says "Girls follow you around a lot, don't they?" or something to that effect. MIL said "That girl -- that was a whole subplot in the book that they left out." But she didn't want to get into it when the movie was on, and I forgot to follow up. So can anyone tell me now, what was the deal with a young woman, Mexican, IIRC, crushing on/stalking Cal? Was it important to the plot, did anything come of it?