My beloved MIL has recently undergone surgery for oral cancer, she had was advised against having her lymph nodes removed as the surgery would have been too long and arduous at her age ( 81), they removed the cancer, she has a temporary plate in the roof of her mouth and a skin graft etc ( top of her mouth), she lost most of her top teeth and gum). Got results yesterday and was told stage 4 has gone into bone. When she had her scan before her oral surgery of her head and neck the radiographer noticed a suspicious legion on her breast, so she was referred for investigation and had biopsy/scans etc and has subsequently been diagnosed with stage 2 breast cancer. , because the oral cancer is taking priority she has been started on hormone therapy for 3 months. The oncology team ( for oral cancer) recommended a 6 week, 5 days a week course of radiotherapy), my MIL initially said no the side effects she was told about sounded horrendous, but my FIL we feel is pressuring her to do it, she is now saying she will do it. 
To put the situation in context we are living in Ireland but came over for her surgery to the UK, my SIL( lives in uk) has offered as have we to attend all the medical appointments but they ( mainly FIL ) are refusing us to go so we don’t feel we are getting a full picture of what is going on, what her prognosis is etc, they are saying the 2 cancers are unrelated, there is no cancer in her lymph nodes but she has stage 4 oral and stage 2 breast cancer. 
I know I’m rambling but we’re at a loss how to help her/them.