My sister is a pathological liar

11 years ago when I was 13 I met a girl named Hannah on MySpace through my sister. I only ever talked on AIM and MySpace until one day she texted me (but these were flip phone days) so we rarely talked via text. Well, one night I went to my sisters house (she's 12 years older than me) and I found a track phone there that was the same number and on my sisters computer were aim chats with me and my friends........
My sister has been lying about being in college for 8 years... She still has zero degree to prove it and no one knows the name of her college... For the same 8 years she has been telling us she has cervical cancer so she had a hysterectomy after she had my nephew. Then it turned into breast cancer this year but miraculously disappeared because of using chemotherapy in the form of a pill and shot at home. She was never in a hospital or did chemo at a center...
Now, today, she tells us she is pregnant and it happened because she went into remission and they discovered they didn't take out her entire uterus??? She said this same thing before a few years ago and the timing is just perfect because BOTH times it was when my husband and I were TTC but we have fertility issues and have had zero success. The only 2 times I have ever mentioned it and she conceives miraculously?😒
If I confront her I will never see my nephews again, she won't allow it. She is mentally ill; she has serious issues but she has some great qualities aside from her constant lying. I see straight through her... But if she has another miscarriage (she claims to have had 7 before her "cancer" but no proof or ultrasounds and no ultrasound pictures today when she told us either) I will lose my shit with her lies.
My mom is finally FINALLY realizing the bullshit but we love her... She just needs mental help... And I'm scared my nephews wont be allowed to see me if I ever address it because she believes her own lies... That's the scariest part...