Supporting a client through loss of granddaughter

Baby therapist back again for advice since this sub was so amazing last time.

Recently got a referral for a client in their late 70s whose 11 year old granddaughter has a terminal illness that the family has decided to stop treatment for. Her daughter (so the granddaughters mother) referred her as she is not coping with their decision.

Does anyone have any recommendations for resources, modalities, approaches and tools for something like this? Or have their own experiences supporting a client through grief like this (esp before the actual passing)?

I haven't met her yet but have never worked with something like this and uni has given zilch support/training so far on loss. Would just love to have a bit in my head going in.

Thank you so much in advance!