Friend Has Pregnancy Delusion

I need some advice but also just a space to rant and see what anyone knows about this. I'm going to change names and relations in the situation for privacy reasons. TRIGGER WARNING FOR PREGNANCY LOSS AND MILDLY DISTURBING DETAILS OF LOSS.

My friend Danielle has had a total of 11 miscarriages in a span of 2 years. But they didn't actually happen. There were never any pregnancies. She has named these children and grieves these children because she truly believes them to be real. Danielle talks about them all the time and even has supernatural experiences with them. I was shown the pregnancy tests that she believed to be positive but each time, they were clearly negative even with multiple tests at a time. She told me her doctors never saw anything in ultrasounds besides revealing she had growths (I think cysts) in her uterus a time or two. She even told me blood work came back negative. She was adamant the doctors were wrong and it was actually a baby each time or came to the conclusion she had already lost it. She swears she has symptoms and has late periods.

She has sent pictures of what was clearly discharge or period spotting thinking it was her "baby" and keeps it on a shrine display in her room. It seems as though her pregnancy announcements and losses line up with the pregnancies or births of her friends or family members. I believed her at first but now I'm just annoyed and disturbed. Every bit of evidence is stacked against her. How do you tell someone deep in a delusional belief that you no longer believe them? I'm not even sure how this started for her but Danielle does have a history of mental illness and lives in very poor conditions. History of psychotic behavior is present. I would worry deeply if she were to actually have a child. I don't know how to be supportive anymore without feeling weird about it. I care for her but it's just too much. Believe me, I understand that I have some poor boundaries and communication skills to have not said something already but I just can't fathom how I would feel if I were her