Tiffany is currently NED, and could, theoretically, stay that way her entire life. Tiffany may or may not ever get a recurrence. Komal's cancer, however, is always there, as far as I know. She has never been told she is NED, as her cancer is from a gene mutation that is always there. Her cancer is not curable because the gene mutation causing the production of a certain immnunoglobin is not reversible, and, eventually, it will end her life.
Tiffany's cancer was a tumor that metastasized, and that has been successfully treated to date.
Now, I do find Tiffany to be a bit gaunt in certain videos though she has gained weight overall. Namely, the area around her eyes seems to have permanently hollowed out. Her hair, however, is her best feature in my opinion. Why Tiffany didn't wear exercise-type clothing to go on that walk with Matt suggests she hadn't planned to exert herself physically or exercise. Matt, on the other hand, was doing a practice run for the hills!!