Hello there @chuuuckie
It makes me smile when I hear/see people's interest in psychology :)
I am sorry to hear about your grandmother. I also know an elderly lady who lost her soon to physical illness after looking after him for many years. It must be an unbearable pain to endure. Still, one should not give up for the sake of those who are still around. Love, attention and companionship normally help to uplift sadness and despair. But, because your granny's mind is clouded by the negative thoughts caused by her depression it is difficult for her to notice this. It would be wonderful to find ways to make her notice the love you all have for her :)
While medication is greatly helpful in cases like that of your granny's sometimes they are not enough to deliver a long-term solution.
Thank you for your comment & congratulations for becoming an engineer soon!!