Hi Angel,
Your friend's experience brings back my memory of my situation 5 years ago. Like her, I was hospitalised half way of the treatment due to high fever and other complications. Like her, I suffered from depression, but after the treatment was over. When I was receiving treatment, my mind just focussed on beating the cancer cells and had no space for depression. Your friend may not feel like taking medicine to cure the depression. I refused professional help too when I was seriously depressed because I thought that I could handle it myself. When the situation got worse, I was always thinking of killing myself to end all the sufferings and pain. I ended up with a one-month stay in the psychiatric ward. I had daily psychiatric counselling and anti-depressants to help me, without which I think I am no longer alive.
So try to keep a closer eye on your friend and if necessary, talk to her doctor and see if anti-depressants are necessary. Depression can be more dangerous than cancer, sometimes.

Karen