This is not a cancer you want to die from, it is a very painful and ugly way to go. Open fistulas draining pus and other liquid debris from the decaying tissues in your face, inability to talk, eat, and more. Opiate pain meds will make her non communicative and non lucid towards the end. Metastasis, if you are lucky, to brain or other vital organ that finally kills you, and the pain and consequences of a distant cancer added to the equation. Stage 2-3 tongue cancer is very survivable. There is no guarantee that she would make it 2 years and certainly not at the current level of quality of life without treatment. You need to convince her this is a bad idea if you can, though ultimately it is going to be her decision.

The problem will be when it gets so bad that someone decides they have made the wrong decision (not to treat), it is too late for any treatments to be effective.

Palliative care will be pain management, chemo will barely put a dent in it without radiation to go with it, and of course Cisplatin or some chemo like it will make her so sick that she will have no quality of life. Things will not stay the way they are today. She needs to understand that. At least the discomfort of the treatments has a positive outcome for most, particularly stage 2 patients. She will have worse discomfort and no future if she follows through with this choice.

I'm am sorry about the blunt and graphic description I have provided you which is all true. But I felt it necessary to state it clearly so that the idea that the next two years would be pleasant would not be her thinking, as that is not reasonable to expect.