I am so sorry.
I have seen this happen not infrequently in young hamsters and I look on it as almost like a cot death. I think there may be some small abnormality in the brain that causes a blood vessel to burst and the hamster suffers a stroke.
There is one tiny ray of hope though in that if you can get her through the first 24hrs after a stroke some hamsters will actually recover. They may have a slight disabillity but they do survive and live a normal life.
You need to keep her hydrated and maintain her body temp as she will be unable to do this herself. Use rehydration fluid like dioralyte and try and offer porridge or babyfood on a spoon. Massage her tummy to get her to wee and poo. If she does not do this I would advise you to take her back to the vet tommorrow as if she cannot eliminate then she will be in pain. Use either a heat pad of a warm hot water bottle.
If you feel in your heart she cannot make it then you are very brave to let her go. I doubt it was a fall ans the shelf is not so high in a heaven and if she was in the ball it sounds more like a stroke.
I am thinking of you and feel so sad that you have had to tackle this when she is so very young but I think she was sent to you because it was known how much you would care, support and love her. Is is nobody's fault. What will be will be.
If her time has come may her path be gentle and paved with love. You will hold her paw all the way.
I don't know if this helps but here is the story of our Lola who we lost very young
Lola