The film is kind of recent (2000-2015 I guess). American or European.
A girl lives with her dad happily, the dad would pamper her and play with her all the time. (I think their apartment might look like a playground as well.) But she also misses her mom.
During the film, the dad would take the girl to a clinic, the girl thinks her dad is sick, but the doctor would then check on her as well, making it look like a casual check-up.
The doctor tells the dad there isn't much time left. I thought the dad is gonna die.
The separated couple sort of get back together for her birthday or a trip.
The ending: little girl falls asleep in dad's arms, then the dad starts to cry because she's dead. Didn't see that coming at all.
So the girl lives her short happy life without knowing she's dying.
Thanks in advance.