Hi Mares canteen offer a great book for 12-24 year olds http://www.canteen.org.au/cancer-in-my-family/mum-or-dad-has-cancer/
get her to have a look. There is also a book from cancer council about talking to kids.
http://www.cancervic.org.au/downloads/brochures/CISS_brochures/Talking-Kids-cancer.pdf ;
She will be worried about you . My kids were 8,10 & 12 when I went through treatment ( 10 years ago) and they helped set rules for the house! I did contact their school and the teachers kept their eyes open. If she needs help you could get a referral through your gp for a mental health plan. Dont be afraid to get her some one of her own to talk to. Even if it is another adult, family friend that she is close too. Good luck with everything. Hugs Jo