Wanting some advice please???

Hello my grandma has just been diagnosed with stomach cancer and I'm struggling to understand why or what's caused the cancer ??

We have to go for a CT scan on the 18th to find out how far along it is and what treatment she's going to receive x

It's all started happening since January she's lost weight doctors just kept saying she's anemic then she went for camera eventually last week and they took biopsies and we got the results yesterday and they said she definitely has stomach cancer

How do you cope with a loved one who's so I'll with this and what can you say or do to make them feel a little better??