Hi and welcome to the Chiari forum.
As Lora suggested it could be sleep apnea...but pain will also tire us out as well...u stated she has had pain since surgery....
Do u know if she has ne related conditions? Having Ehlers-danlos can cause some major issues post op especially if she has CCI...ceriocranial instability...having decompression weakens the spine where it connects to the skull....with this area already weak from EDS it can be a miserable experience post op. A Cervical collar may be of help until things are figured out.
Other post op issues could be cerebral ptosis, or rejection of the dura patch....
She needs testing to rule out ALL related conditions....know it may not be due to surgery at all....
There are a few things that could be going on individually or all at once.....
Ur sister is lucky to have u to advocate for her ....
Are you sure its narcolepsy and sleep apnea? I was constantly falling asleep also and went through a sleep study where they discovered I had sleep apnea. I only ask because my NS told me that sleep apnea is one leading cause for chiari. I started using a CPAP and sleep great now.
Sent you a private message :-) Lisa