Night-mares.
This is different than night-terrors.
But it can be a night-terror too... even if she is not thrashing about.
Kids, from about 2, can have night-mares. Developmental based. Even if a kid is over-tired, they sometimes have night-mares.
My son... he makes noises like that at night and then I observe him. He's still sleeping. But he will yell or scream or make grunts. Sometimes, when he then wakes or the next morning, I will ask him about it. And he tells me he had a night-mare. And sometimes he will even tell me what it was about. Sometimes it is even about his day. He's NOT traumatized or anything... but he "knows" he had a dream. I explained to him what dreams are. He is 3.5 years old now... but even when younger, he knew what it was.
My son is a terrific sleeper... but sometimes he has a lot of dreams. Sometimes he will even be laughing in his sleep.
My daughter on the other hand, would sometimes sleep-walk... but she is still 'sleeping.'
Both my kids nap, since they were babies, and even currently.
all the best,
Susan