I just wanted to send a hug and say you are not alone. My mum had breast cancer a few years ago. Treatment was successful but family relationships were destroyed to my mum being a monster throughout. I then lost my father in law to Covid and my best friend at 46 was diagnosed with terminal cancer a year ago. It's now in her lungs, liver, bones, bowel and lymph and chemo is ineffective. My mother in law has now been diagnosed with liver cancer. I've lost so many loved ones through relationship break ups and death that my existing anxiety is at an all time high. I feel for your friend and her children and hope treatment is successful. It's hard but you need to look after yourself including distancing yourself if necessary. If the worst happens you can still be a strong presence in the children's lives but hopefully it won't come to that x