She seems to have a good life, and you did your final duty as we all must. I have hated every such experience, and I know how hard this was ... but there will be a day you look back and smile at all the good times she gave you.
Every good dog needs a successor. Mourn her as you need, but don't take too long to adopt that next one. For every one we lose, there are many who need good homes. Every dog we have had after the first got the chance because their predecessor left.