They can't do that. They need a B visa to visit.
And based on the fact that you posted this on the 'Bringing Family Members of US Citizens' board, you will need to petition your family member properly. They cannot visit and stay to adjust.
In this case, CR-1 would have been a much smarter choice.
If you need to travel, I wouldn't rely on advanced parole. There is no guaranteed timeline, and it is not a substitute for a green card.
That isn't it at all. US citizens have been scammed for green cards by people from third-world and developing countries. It pays to be vigilant whenever there is a large difference in equity in a relationship. Many of these marriages would never happen if living in the US was off the table....
So does filing a fiance visa petition without being completely sure. After all, it does require intent to marry. It is not a "try it out and see" type of deal.
It was intended as a way to explain why it might take longer. And it is true- many of the reasons for delays in the AOS process are not present in consular processing. OP made that choice, it’s a trade-off.
But was yours an entry on a visa? Instead of petitioning her, she entered the US and is adjusting status, which is a convenient way to bypass the long queue in Montreal.
It’s just bizarre to even bring it to the attention of the airline/your country’s passport control.
I agree with Crazy Cat, for other people reading this: do not do this.