What causes this and is it serious? thank you so much for your help!

This is what she wrote:

"You know when you wake up, and you haven’t a clue who or where you are? Happens to me all the time. I wake up confused, and I say the most stupid of things in “reply” to someone who is talking to me, only to find there is no one there. I walk to the top of the stairs and I shout down to say something to my dad, and he’s like, “what are you talking about?”. I have woke up thinking I am in a hospital, I am in another country, in another house, or not in a house at all. I have woke up forgetting what my name is and sometimes even thinking I am not human. Bizarre. It’s all really bizarre. This happened to me this morning, I woke up in such confusion I was almost in a panic. It doesn’t last long, only lasts a minute. Maybe I am still “living my dream” (or nightmare, in some cases) when I awake, but sometimes I can’t even remember the dream before I woke up."