I ran around as an adventurer for awhile, killing things near where I planned to build a fortress so as to see the results in the future engravings. I wanted to kill her off before the end of the year 1049, so my fort would start neatly in Spring 1050. (By the way: the 14th of Obsidian appears to be the last day possible to end adventurer mode and have the next fortress start up the next year. The 15th or later, and I got Spring 1051.)
There was a nearby body of water that froze at night and thawed in the day.
I sent her out on the ice sheet at night and told her to go to sleep.
She woke up on land. You may recall people complaining about "sleepwalking"; well, it happened again.
But this time, there was a sea serpent, too. It must have interrupted her sleep. And it was somehow on the other side of my adventurer from the actual water. On dry land.
Air-drowning.
. . .
So, like I would expect from any good dwarf, I told her to get up, hack at the sea serpent with an axe until it collapsed in pain, then slash its throat over and over and over again until five different openings were ripped into its arteries, watch the serpent bleed to death before her, butcher it, collect its skull and scale, drink its blood, eat one chunk each of its meat, heart, brain, lungs, intestines, and all the other available organs, and lick its nervous tissue.
Then go back out on the lake to die.
--Rexfelum