Pregnancy due date question !!!

Tayler

My brother had a fling back in beginning of April and the girl said she was pregnant with his child up until now. Now she’s saying that the doctors are moving up her due date 8 weeks and that it’s not his. Could the doctor really have move up the due date that much at 18 weeks and say she is actually 26 weeks? Her original due date was beginning of January and now she’s saying it’s going to be November!