I'm very sorry for your loss

and I agree with the others about the time line for grief. I think it's natural to have to many questions and go through the 'what if's'. I don't think you not speaking with her when you did, had anything to do with her decision. I believe they are very sick and we can't blame them for their decision. They feel a terrible pain...they're tired and want it to end. I don't believe God will punish them for being mentally ill.
My brother took his life 2 1/2 yrs ago with alcohol poisoning. At 1st I was angry and shocked. Then the morning of the service I was getting ready to go to the funeral and discovered by reading in the paper

- that my SIL had him cremated before we got to see him. My oldest brother flew 4 hours and never got to see his brother. I'm like you - I desperately needed to say good bye and get closure -I was denied that

. I was livid and couldn't even go to the service because I was afraid of punching out my SIL
I called her and told her how shocked I was, that she didn't give us the chance to see our brother and you know what she said - " Oh me and my daughter, can't stand to be around dead bodies". What a poor excuse. She could have told me and my siblings to come when she/daughter weren't there, so we could see our brother one last time

. So I was shocked by my brothers suicide and then stunned beyond belief at not being able to see MY brother - just like I was stabbed twice and then have vinegar poured on it. Sorry for the venting.
I came here to PC for a marriage problem, but talking here about my brothers suicide helped me a great deal. Talking took the shame out of the whole taboo of suicide. I share my story is hopes that it will save a life. I realized that I have a gift, of being able to reach others in their time of need. I'm sorry that my brother felt compelled to do this but I won't allow it to ruin my life. You also will come to realize, you can make peace with your sisters decision.