I don't know why they have a difference. I saw with my own two eyes that my mother were really given 2 diamonds on her Daily Challenge. I also contacted Customer Support and they just told me this:
"All rewards in Enchanted Tales are random and are determined by a number of factors. These include player level, number of items unlocked, and in which order they were unlocked."
I don't understand what they were talking about the number of items unlocked. Do you think it's the decors and buildings?
My mother's level is still below mine and she has been receiving the 2 diamond reward ever since.
When I start off the game, I get the daily quest with 3x75coins + 1 diamond. Then watch 5 movies then will get 5 diamonds.
Then when I progress, the dialy quest become 3x25coins + 1 diamond. Then watch 5 movies then get 75 coins.
Then progress until today... i only get daily quest 3x25 coins + 1 diamond. No more watching movies thing.
So I am not sure the update cause this or depends on level.
Just want to share this.