In general, I think it's okay to lie by omission when you are not ready to tell your T something. As my T has said before, it's okay to keep secrets from her.

BUT, in your case, I think it's different because this is something that is dangerous and could cause serious harm. I understand the fear of telling your T, but I think it's important that you do.

Recently, I told my T that I used to watch her out the window of my dorm as she left work. It did feel a little disingenuous and not fully "right" to go on and not tell her. I had the same thoughts: what if she wouldn't accept me if she actually knew? What if this relationship is built on a lie since I'm not telling her this horrible thing that I've done? Well, she took it so well and told me "there is nothing that you can say that is going to screw this up." I think you may be surprised at how much your T would not be angry, but truly care about you if you were to tell her the truth. For me, telling my T really showed me that she will accept me no matter what. This was something I could never fully believe until I actually experienced telling her one of the hardest things.