By now it is known that Eilish
passed while she was sleeping, which is referred to as "dead in bed syndrome." Ann Bartlett wrote a very complete piece about this on HealthCentral:
"This week has been a difficult week for the diabetes community, when it was revealed that young girl of 13 never woke up. There have been 4 deaths of type 1 teens recently reported and many of us remember Cynthia Kahn who passed away earlier this year. We have lost some great people simply “while they were sleeping”, which is commonly referred to as “dead in bed syndrome”. It is always alarming, and probably more disappointing that we don’t have an answer for how someone, in otherwise good health, could go to bed and never wake up."