I'm sorry Kitty. That's so tragic.
The fact is, at this distance, you can never know - none of us can - your daughter was ill and it may be it was always going to happen.
Sometimes life is hard - I can't begin to explain to you why some of us have long lives and others of us don't.
as tragic as this was, what might be even more tragic tho is if you spend the rest of your life punishing yourself for this.
Have you ever had counselling for this? it might help you get through your grief and guilt.
You have a lot more living to do - what about making the rest of your life as something you and the spirit of your daughter can be proud of?
D