Welcome!!!
Unearned guilt sucks, for lack of a better word. Perhaps you have some abandonment issues, you feel like you're abandoning her, 'leaving someone I love to the wolves'. You have to tell yourself, over and over again, that you have no control over her actions.
Work through the grief steps as much as you can, and do try to look at that abandonment thing.
Keep coming back, you'll find a lot of support here.