I'm sorry to hear about the loss of your loved one. I very recently lost a family member to cancer, too. I can't say that I know how you're feeling, because I don't. I can only say that I understand the sorrow, the anger, the confusion, and sense of loss you are feeling right now.
The best advice I could give in a time like this is take some time for yourself in the near future. Once all the family services are past and the visits and phone calls are done, that's when it really hits home. The FOREVER of it all. I suggest taking a couple days just to yourself. Do some of the things that you two enjoyed together, and instead of surrounding yourself in sadness, make an effort to be HAPPY. Let it be your very own celebration of her life with you. Be happy for the time you two had together. Be happy knowing her suffering is at an end. Be happy in the knowledge that you'll be together again.