Your grandmother sounds like she was an amazing woman and she seemed to have raised some really good kids, the love and family bond is so clear. I'm happy for you that you could take care of her last weeks, but I'm sad for you that there was a traumatic experience involved that night. I hope you were able to (partially) process that by now.
I always think it helps when the people they love tell them it's ok to go now, because it often seems they are not ready to let go because of the fear that those left behind aren't ready. This is one of many stories where I read (it also happened with my grandmother btw) that once the closest to them tell the dying person "it's ok to go", they are ready to leave.
I know it's not been too long since this happened, I'm now heading to your latest post and maybe find out how you're doing .. it's a lot, and it's ok not to be ok if that's the case..
Much love..