Complex sentence: Later in the movie, Holly didn't seem to have a problem when Greg sneaked in to the Country Club, when Greg saying he wanted to hang out with her, almost revealing his feelings for her, Heather Hills comes by and interrupts.
Split into simpler sentences: Later in the movie, Holly didn't seem to have a problem when Greg sneaked in to the Country Club. When Greg says he wanted to hang out with her, and almost reveals his feelings for her, Heather Hills comes by and interrupts.