There are two schools of thought regarding half-staffing the flag. Some say "if it feels good, do it" because they don't care much for rules. Others point to the United States Flag Code that gives the authority to order half-staffing to 1) the President of the United States, or 2) the governor of each state. I think if you asked the general public, they would oppose half-staffing the flag for a family member unless it was upon the occasion of their body being shipped back from a war zone. Deaths of police or fire fighters occasionally rise to that status as well. So unless your aund died in the service of her country, I would vote against half-staffing the US flag. I recommend you drape the front door of her / your home with a length of black ribbon as a sign of mourning.