You can tell how much you and Sheba meant to each other and it sure shows how much you hurt over her passing. Please know that you did all that was right for her. She knows how much you loved her. ((((Hugs))))
As for replacing her, nope, you will never find one that will do all she did for you. Sheba was special and a rare one of a kind gem. But keep in mind that there are others that if given a chance can be just as special in their own way. Definately hard to do and something that I have personally struggled with at times. I sometimes think that it is us humans that have a hard time allowing the others to be just as special in their own unique way.