Sister just diagnosed with Lung cancer

My sister was just diagnosed with lung cancer she is 63 years old it has Spread to her lymph nodes and her brain (there are multiple tumors in her brain )they are doing a pet scan tomorrow to see if it’s anywhere else. She is also very confuse so it’s hard to talk to her. I think she’s so confused she doesn’t even realize she has cancer. Which is probably a good thing because she is very high anxiety with her health. I have a question because this is so new to our entire family if she asks what’s wrong with her she should actually tell her? I know it wouldn’t be right just to tell her everything is fine but to tell her she has cancer I even have a hard time just saying that word now. He also said she had a mini stroke which they were not able to give her medicine for a stroke protocol because of all the lesions in her brain. Any comments or thoughts would be helpful thank you