Four-year-old Crimson suffers from an illness that attacks the brain stem.
It is called Diffuse Intrinsic Pontine Glioma or DIPG.
Family members say Crimson's tumor is inoperable because it's in a spot where all of the major motor functions take place.
Loved ones tell us they are now trying to cherish the little time they have left with their little girl.
"You are trying to make the best life we can until she goes," said Crimson's grandfather Ron Huffman. "You know that's all you can do with this."
Crimson was diagnosed with the deadly disease at the end of November.
Family members are asking the community to send letters and cards to the little girl so that they can read them to her over the holiday.
If you'd like to send a letter to Crimson, the address is:
Crimson Barnett
PO Box 15367
Fresno CA 93702