Bjorn's right. The TSA people generally won't even know what a riser is and whether it should be allowed or not. They make a snap decision and whatever they determine is the "rule" of the day. One might not look twice at it, the next might toss it out. Trying to win that arguement while trying to catch a plane could turn into an excercise in frustration.
The bottle of Kahlua probably shouldn't have made it through. Just another good example of sometimes things do, other times they don't.
Shipping ahead is the safest, beyond that I would put it in checked bags and hope like heck it shows up. A backup riser in your wife's bag would sure be good insurance.