It is difficult to pinpoint the age at which children begin to have nightmares (or dreams), as we have to wait until they have words to describe their experience. But by 4 years many children have them. Since she doesn’t seem to be fully awake, I would just pat and soothe her (or hold her for a few minutes) until she calms down and returns to sound sleep. Then the next morning, ask her if she can remember having a bad dream and waking up. If she doesn’t seem to know what a dream is, say something like, “You know, a dream is like a TV program that runs in your head while you are asleep. Sometimes it is scary. Do you remember yours?” If she can recall any content, show interest but don’t ridicule her fears. Then offer reassurance, “Things that happen in dreams aren’t real, and a lot of times they don’t make sense.” If you can think of one, tell one of your recent dreams.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.