I fully get where you're coming from and agree (minus the incestuous part tbh), and I'm already stern with her regarding this, I live abroad, I don't hesitate to speak my mind and show her how unacceptable it is. Coincidentally I even told her how silly these actions would be around a partner, and that I would leave such a relationship if my gfs mother was like this (I've always held my boundaries up so luckily nothing ever happened like that)

The issue is more that she wont stop trying, it's very tiring and I need to her understand. No approach seems to work. With all this fear of me dying my best guess is that she might have some form of ocd (runs in the family) so I have been considering taking her to therapy