Is dying in your sleep rare in a 23 yo female?

Extremely rare. More concerning is why, at age 23, you would be concerned about dying in your sleep. If this is a preoccupying fear that you find yourself obsessively worrying or perseverating over, this could be a sign of depression, anxiety, OCD, or other psychiatric problems. In someone with a profile that mentions depression and anxiety, such as yourself, I would worry that better control of those is needed.
Yes. In an otherwise healthy 23 y/o woman (who does not have heart/lung/blood vessel problems, unknown aneurysms) dying in your sleep is VERY, VERY rare. Hope this helps. Best of luck. Dr R.
Yes. Incredibly rare. I don't even think I've ever heard of a case that wasn't associated with alcohol or drug abuse.