Jenny,
I am so sorry to hear of how things are going. Treasure the time you have now. I lost my best friend earlier this summer and while it was so hard to let go, I couldn't bear her suffering. What started as everyone being hopeful and hoping she could hang on as long as possible evolved as her disease progressed to where we could tell her it was ok to let go and truly mean it. I don't think you need to ask God for forgiveness for feeling as you do. I can't think of any words to lesson the hurt, just know that there are lots of people here caring about you.
ilene