L.A.
Does she give any reason? This sudden high level of fear sounds like she had something happen that scared her. I'd suggest asking her to describe the "bad" things that could happen and then together you rate them on a scale of 1-10 for how likely it was that it could happen. Then put together a plan for dealing with each scenario. Maybe if she feels like she can handle what happens it'll be easier and maybe during the discussion she might give you an indication of why she's suddenly so fearful. It's not typical for a child that age to be so afraid. If this doesn't work I'd ask your pediatrician for a referral to a family counselor who deals with kids with fears.