Obviously she would need to have a C-section...but as long as she’s delusional...I see no reason for aborting it. However, get the girl to a safe place where she has someone watching over her.
I have a feeling the pregnancy hormones are making her feel good and that is why she says she “feels happy”.
If she had the baby her mother would have to raise it as if it were her child, we all know this. I’d hope the grandmother would be willing too