My heart goes out to you on the loss of your neice. You sound very traumatized and it's understandable to have such a reaction after something so terrible.

I believe I can relate in a way. My child became very ill when he was young and I never wanted to admit how terrified I was that I'd lose him, I couldn't face the thought of being without him. (He is fine right now, don't worry) but it's a lifelong concern. Letting my kids out of my site became a sickness. I've gotten better in some ways, i don't hold my kids back, but it's very hard to let them out the door sometimes. I wish I had a concrete solution but I think therapy might be the best option. You can't go on feeling like this. (Advise I need to take as well)