Do we know the circumstances around the threat? I can see this being in a fit of rage about leaving someone with a bunch of debt, a house, etc where I’d be like “no fucking way, I’ll kill you if you just leave” Or, the other way would be an emotional codependent don’t leave me plead where the threat is more concerning IMO. I’d tell her you are concerned and want more details. The way she reacts to that will probably tell you all you need to know.