YUCK!!! What a gross, hilarious and frightening thing to watch!
My oldest daughter had a period when she would be awake and dreaming... seemingly alert, walking around and talking to people, but definitely hallucinating. Most of the time, it was certainly a fever that was behind it, but a couple of times (she probably did it 8 times over about 2 years, not as close together are your daughter's, except one week when she was really ill) it just seemed that something had gone wrong with her ability to stay still while dreaming. I put it down to stress, as it always seemed to happen at the worst possible time for everyone.
Perhaps your girl is in need of more rest during the day (the counter-intuitive solution I've found really works for poor nights), so she's not so exhausted at night. Being overtired makes all kinds of things go wrong.
Of course, whatever is making her throw up may also be making her hallucinate. Some kinds of food poisoning do that to people, and the smaller they are, the more pronounced the effects are.
I'm not surprised she doesn't recall the events, as it is almost impossible to remember dreams unless you wake up during them. With her falling right back to sleep, it would be the same as having been still all the way through. What I mean is: I wouldn't be alarmed at all about the fact that she can't remember the dreams.
One thing I found really helped with night-terrors and other frighteningly-realistic dream experiences was to ask *really* stupid questions, like 'are your eyes brown?' or 'what is your middle name?' that they certainly know the answer to, even asking them using the wrong information -- asking a blue eyed child if her eyes are brown works better than asking her if her eyes are blue... it just seems to engage a different part of their brain and pulls them out of it really quickly. I suspect that anything that was a genuine surprise would work, because I think it's the surprise factor that works...