For four years she remained silent, holding everything in.  In fact, there were only two people who suspected that something bad was going on. One of these people was Harry.  One time, Hermione's superior got mad at an unfinished report. Her explanations didn't help her. She said that the day before she left at midnight and that she would finish the report in two hours. He became  furious and started throwing things in his office. Previously, such things had already taken place, attacks happened regularly before the end of the month. House elves were always witnesses.