L.R.
While kids do go through phases where they fear the house will burn down, or a plane will fall from the sky, what you are describing here sounds far beyond those kinds of normal fears. I agree with others saying that she should have an evaluation for possible generalized anxiety. Please ensure that your pediatrician refers you to a specialist (the specialist should do this, not the pediatrician) and be sure the specialist deals with children her age -- it's vital to have someone assessing her who knows how to work with a child her age.
You do not mention how YOU react and what you say or do when she says these things. I can only imagine how this is all upsetting for you, and yes, even frustrating -- at some point, any adult would want to say, "Good grief, you're fine, cut it out!" So please do not feel guilty if you have felt that way yourself. But be sure not to dismiss her fears, as that can make things worse for the child, who feels that "no one is listening to me."
One other thing you don't mention -- Have there been any major life changes in her world in this past year when she's become so anxious? For instance: A separation, a divorce, a new partner for mom or dad, a new sibling born, an extended stay by someone new to the household (did grandpa move in with you?), starting school, any large change like those? Major changes can rock a young child's world in ways adults don't always grasp, so it is vital to think through whether she has experienced any such changes; she still should get a professional evaluation and possibly therapy, but knowing if a change might have kicked off the anxiety is important information. The therapist or psychologist should ask you about that, for sure. A child who undergoes changes often starts to demand more attention in any way she can, so if there's been any big change your child might have discovered that anxiety can get your attention focused on her. But even if that's the case -- I would get her evaluated ASAP because it's gone beyond just seeking attention.
