Film rating for our film

Our film would have a rating of 15 as it contains a dark theme. It focuses on  Sarah, the main character and her state of mind which lead to her disappearance. I think that the masked characters would probably scare children under 15 as they tend to appear out of nowhere. The fact that they are a pigmentation of her mind shows that we have to create a way of making them appear dark and mysterious. Also I think that it makes it harder for younger kids to understand what she's going through. Not that many teens do actually understand Sarah's situation. But I think that it they will relate in the way that Sarah feels, her loneliness and how she seems to handle her life. I think that 18 is too high a rating as the masked figures do not present any threat to anyone else but Sarah. They don't attack her in any way or harm any of her family. I think that she is a young teen who has a mental problem that she needs to overcome.