There is no good advice in my opinion. Losing anything that meaningful is going to hurt no matter what.
One thing I will say is you never regret the moments you spend with something you love. As much time as you can devote to her, do it, it will not be a regret.
It may also help to be positively patient with yourself. Realize that it is going to suck and you are going to be hurt, and there is no time table for it. It will take as long as it takes for the grieving process, and there really is no arbitrary measurement for how long it takes to get over it.
She truly will be in a better place. Whether that be heaven or not suffering, she will experience peace. She won't be in agony every day. I think we all have a point where suffering is no longer preferable even for those we love.
The last thing is remember you were the center of her world. She loved you immensley and love will always stay with you. And do not second guess forgoing chemo. It is not a bad decision. She is going to need you and I have always found that we can learn lessons from death about a life well lived. She will pass with people around who lover and love in her heart. That is something to be revered.