You may also want to check out if she is hearing scary things from other people or sees anything upsetting on television, has she siblings ,that may tell her scary things and if she is senstiive it may upset her.check out what is happening on a regualr basis in her day.
binnks is correct - you really need to seek medical help - a psychologist or child psychiatrist or child neurologist. I suspect strongly your child is suffering from GAD - Generalized Anxiety Disorder (a very common anxiety issue) and your daughter will require assistance to help her overcome these issues. Let me assure you - if anxiety is the issue, your daughter will not outgrow it nor will it go away. But, the longer treatment is delayed; the longer the recovery tends to be. Please call your family doctor and ask for a referral to a medical specialist with experience in anxiety issues (three examples of specialists are listed at the top of my posting). I wish you the best ....