A colleague asked me if STBX has a substance-abuse problem today. I'd never thought of thinking that. But a fella he knew with a Wayward Walkaway Wife who cycled the same way STBX does later discovered that his Former was a raging, but closeted, alcoholic. Hmmm.
I've always felt, from reading all of your well-documented interactions with her, SP, that it's either substance abuse or some sort of mental health issue.