It is true that Jinn can sometimes interfere with our lives. However, they cannot father children with human women. Allah says: “He has made mates for you from amongst yourselves.”
Therefore, her child is doubtlessly from a human father. If she was not married, then she may have been raped and is ashamed to admit it or she may have engaged in some unlawful act. Since you do not know which of these two possibilities is the case, you must not lay any blame upon her.
And Allah knows best.