went round my nans today and my nans cat who is called felix and is 14 is dying

as he is collapsing on the floor and is in the corner dribbling on his side and it looks as though he has gone blind as when we wave our hands he is just staring not one movement in the eye and he is so skinny my nan is really upset. he cant even move he is breathing thats it he aint even driniking water. we are calling the vet tommorow to put him to sleep but my nan doesnt want to do it i dont know why. we explained he is in pain but she is finding it hard he was her first cat and is so lovely. will miss him