probably should have added, 21 year old female.
It sounds like she has Sleep Apnea. A person stops breathing for a short amount of time and then starts back up again. She needs to go see a doctor and have a sleep study done. She might need to wear a mask that forces air into lungs to prevent it.
At night, this sounds like sleep apnea. Nightmares, dissociative behavior, confusion -- it all matches.
However, the daytime syncope is troubling. Syncope (which is a temporary loss of consciousness), is not associated with sleep apnea, but could come from a variety of neurological or cardiac medical issues.
The best way you can help her is to convince her to see a doctor about these two problems.
Possibly epilepsy. That's serious enough to need attention. She shouldn't be driving if she can pass out. Though talking during a seizure would probably rule it out, as would the distinct pattern of every night.
... why won't she go to a doctor? That in itself is unusual. Find her the type of doctor she's comfortable with - maybe female, younger, older... go with her...
How are you sure that it's "absolutely not sleep apnea"? Along with Obstructive Sleep Apnea, it could also be Central Apnea. You thankfully are her advocate, observe closely what is going on, and report what you see. I have my wife to thank for no doubt saving my life. She urged me to get a sleep study done at our local hospital which revealed extreme Obstructive Sleep Apnea. I got on CPAP and am fine today.
Update. the no-breathing episodes have mostly quit. Now it's worse. I believe she has Dissociative Identity Disorder. All the signs and actions point to that. The problems is that she is so scared to go to a doctor because she doesn't want to be called "crazy".
How do I talk to her to convince her that she needs help without scaring her more. These episodes are a hundred times scarier than when she quit breathing. I talked to her "alter" last night for at least an hour before she went back to being herself. She is extremely scared to even hear what happens during these episodes.