Well, there are many benefits to befriending Marnie. You get valuable items and interesting cutscenes as well. While she might seem too occupied with her hectic schedule, she can be a good friend to have in town. You can befriend her by giving up to two gifts per week. Giving gifts on Fall 18, her birthday, will also give eight times effect and unique dialogue. Interestingly, you will also witness special cutscenes in her heart events.