Who;; I miss her so much and I don't know what to do anymore?

I’m 14 and I had a nanny, not a grandma a lady who took care of me, and in 88 days its going to be three years since she left and moved home to czech republic. She was my sister, my best friend, and even more of a mom than my mom will ever be. She was the closest thing I had to a functional family. My parents always fight and my brother I never see him. I miss her so much and I don’t know what to do anymore. I have cried myself to sleep so many nights. It feels like its been so long that I cant remember her anymore. I was 3 when I met her and I don’t want to ever forget her. I talk to her through text and webcam sometimes, but thats maybe once ever 3 months. It feels like she is dead but I know she is there and it torchers me. She cant come back to the u.s. because she doesn’t have a green card, so I’ve been told. It wasn’t suppost to be like this, she was only suppost to be gone for three months. Sometimes I wish I could have cancer or something and they would have to let her come and see me before I die. But I’m afraid to die and I don’t know how to handle all this. You’d think I would be over it after 3 years but it just gets harder. My throat tightens and my stomach feels empty when I think about her. I just don’t know how to handle all this. Can anyone give me advice?