There's no way to bring her with you, I guess. Aside from a court battle. Which, no.
I would say find ways to stay in touch with her, if you can. If there's any way you can try to see her, send her cards or birthday presents, anything. Even talk to your mom after a while and see if she'll let you visit or babysit now and then. Try. She's not going to understand for a long time, but it'll be easier for both of you if you at least try to contact her.
And in the end, it'll be better for all of you that you left. You know it in your heart, or you wouldn't have made this decision. In the long run, you have made the RIGHT decision. For you. For her. It's not going to be ok right now, but in the end, it's going to be ok. You're going to be ok. Hang in there. You're a strong person.