Depression is quite common with cancer and should be mentioned to the doctor, as it can be treated and she could perk up a great deal. I suffered with depression for over a year with my cancer and was amazed at how quickly and how much better I felt just by being put on a antidepressant. We're talking, I felt better in less than 24 hours.
Cancer is hard enough to deal with, she doesn't need depression too. It doesn't need to be a death sentence and she needs to focus on the fact that living is worth the fight. I've known a couple of people with Thyroid cancer and they both are going quite strong through and post treatment.
Have your friend come here and we'll do our best to perk her back up for the battle.

)
Hugs,
Angie