Sarah, your heart must be breaking. I hope, though, that you know how lucky you were, to have such a wonderful friend. And she was lucky to have you as well. Your mutual love for one another makes the loss that much harder---but I certainly understand how you can't let such a wonderful friend suffer. I went through the same with my heart kitty.
Just remember her with love, and know how blessed you were to have her. Some people NEVER have such a friend.
I think everyone on GT loved Ailish, even though we never met her.