I believe my friend is lying about her cancer. It's starting to take a really big toll on me constantly worrying about it and I need advice.

My friend said that she had been researching cancers and she explained she had been researching my father's cancer type. She started making remarks about how I should be really nice to him incase he passes, she said it a lot more abruptly than that and a lot ruder. A couple weeks later as if out of thin air she tells all of her friends including myself about her diagnoses cancer. Out of pure worry I did some research about the cancer and things started to not make sense. She claimed she has "myeloma" but myeloma in a young adult is highly unlikely, very rare. Her story starts to get holes in, the things she says do not add up. She started using her cancer diagnosis as a way to bribe people into getting what she wants, almost guilting me and the rest of our friends into doing what she wants. Not only that I've noticed she been using her grieve and loss of loved ones to do the same, over very petty situations, I won't say what the situation was but I wouldn't use the death of my fish to try to achieve what she was aiming for in the moment. I've had quite a few relatives be involved with cancer, all survivors or strongly fighting, thank the lord, so I know how radio therapy and treatment works. My friend mentioned being on private health care but needing to go to Switzerland for radiotherapy though, my aunty who needed radio therapy is on private health care too and went to a hospital in London.  

The purpose of me writing this was purely for closure and clarity. It has taken a huge toll on my mental health worrying about whether I'm a bad friend because I don't believe her. I really want to be open but she isn't very kind, she is very toxic but if I stop being friends with her I won't have any.