Piggyfan, I know exactly how you feel inside. I am still struggling with the loss of Putt earlier this year. Not a day goes by that I don't miss my special girl, but it does get easier and you will reach that stage.
Marble was such a beautiful girl and they become such a huge part of your life. The grief and the pain that you feel now is the unfortunate flipside of the strong loving relationship you had with her and unfortunately you would never have the love you did for her without the pain that comes after they pass.
Time is a healer, try and think of the good times and remember how amazing she was, in time you will find yourself smiling when you think about her as opposed to the knots in the stomach and the sense of loss you feel now and while you will always miss her, the happy memories will overtake the sadness. We never forget the ones that leave us and while they are no longer there, they live in your heart forever.
Massive hugs x x