If she is staying on your points then it should be free. The unknown part is whether they differentiate between member's staying on points vs. non-members staying on points, although I'm not sure how they would track this. I think the majority of the time its been reported that it was free as long as it was a points stay, regardless of who was using the points.
Sometimes it wont show up on the bill, sometimes it will but they should remove the charges when questioned about it.