I Think Shes Faking Cancer???

So my fiancé has this friend. She supposedly has thyroid cancer. Now I would NEVER accuse someone of lying but this woman is well known for lying about stuff like this. She says she’s been on chemo but we don’t know what kind and when my fiancé asked her who all knows she says her husband doesn’t know, her kids don’t know, her friends don’t know, her parents don’t know, the man she’s cheating on her husband with doesn’t know, NOT A SINGLE PERSON KNOWS. Now I understand that some people don’t talk about it, but my fiancé and I believe she’s making it up for a specific reason. Like she’s never talked about cancer, has never had a biopsy, this was something that just popped up a few months ago when my fiancé told her he didn’t want her around us anymore. So we think this is something she made up to make my fiancé feel bad. Because she’ll come over or call and tell my fiancé “I need support. I need you. You’re not calling me or being there for me and I need you right now” when my fiancé asks why she isn’t telling her family she’ll say “I just don’t want to bother them with it” like it doesn’t make sense. My mom, grandma have had cancer. I have a tumor. My dad has cancer right now. Like it’s not a joking thing to me so I’m getting pissy because I just refuse to believe this woman. She has no proof. She can’t give us a doctor name. She said it’s in her thyroid and that she’s lost 70+ lbs but you can’t tell. She’s just...idk. I hate to be that person because when I learned about my tumor, it was hard for me to process. So I hate to be that person to even question someone. But nothing makes sense and she said she has it in her thyroid and mines in my thyroid and nothings adding up. So idk. I don’t want to get hate for this but this is affecting me and my partner a lot.