A random theory regarding the Admiral…
She was captured by the Klingons in the episode named Lethe.
Lethe in classic Greek refers to something along the lines of forgetfulness/oblivion.
In the original series episode Dagger of the Mind there is a character named Lethe. She was sent to a rehab colony as a therapist about ten years after when Discovery is set. Kirk asks her what she did before and she says “Does it matter? That person no longer exists.” She also describes her old self as being “a different person – malignant, hateful.”
Cromwell is meant to be some sort of therapist.
The two actresses even sort of look like one another
Lethe - Susanne Watson
Cromwell - Jayne Brook
So… did the Admiral actually survive, get incredibly angry and depressed about the capture, the war, the Klingons, Lorca, the whole sorry mess, leave Starfleet behind and go off to forget about her past and revert to being a therapist in the middle of nowhere?