Go and see her. Spend time with her. Talk to her. And, especially, if she needs to talk about ANYTHING, let her talk about it. Even if she needs to talk about the possibility of death, LET HER TALK ABOUT IT.
A sunshine box. Make a box that has small presents in it. They do not have to be expensive. Wrap them and send them to her with instructions to open when she is feeling depressed. usually 5-7 presents one for each day of the week.
visit, maybe try and go on a surprise visit and make her laugh and cheer her up, if she's having trouble fighting it try and make her forget about it, if only for a second. Watch her favorite movie and don't treat her as if she has cancer and you're there on a guilt trip, act like she's your cousin, and nothing more