As the driver, you can try to be more fluid with yout operation of the controls -- gas, brakes, steering.
If you are in the habit of pressing the pedals and frequently changing the pedal settings, and your steering is jerky, then all of htis can add up to a very uncomfortable passenger. As the vehicle's suspension increases in stiffness, the discomfort of the passenger(s) also increases. For example, she is able to tolerate the way you drive the family car or minivan, but these have a reasonably pliant suspension system, and the activity you place on the pedals and steering wheel are absorbed by the suspension. But, you you stab at the gas and brake and yank the wheel in your truck, all of this motion finds its way back to your passengers.
I once -- well, it was four or five times then I couldn't take it anymore -- carpooled with a guy that would press the gas pedal very abruptly and speed up to the cars ahead, then just as abruptly release the gas and slow down, only to repeat this several times per mile. IT WAS HORRIBLE. I have a high tolerance for vehicle travel, but I was physically nautious by the end of the commute. And that is just the way he worked the gas pedal. The brakes and steering changes were made in a similar manner. His car was constantly jerking fore and aft and left and right. And, he was oblivious to what he was doing.
Make a conscious effort to roll onto the gas, and roll off of it, as your need for speed changes. Maintain a 3 to 4 second following distance, and watch the car two cars or more in front to see what the traffic is doing. If you see brake lights, slightly roll off of the gas instead of waiting for the car directly in front to apply his brakes before you make an abrupt change in speed. Obviously, abrupt speed changes are needed on occasion and you need to be constantly at the ready to make them. But, if you can adjust your speed by lifting off the gas then rolling back into it, and create conditions where your changes are smooth and calculated instead of sudden and swift, maybe this will solve the trouble your wife is having. My guess is that it isn't just your wife, but since she is with you the most, you see (or hear) her comfort level going down.
I'm in no position to be judging your driving style, but my own experience with car sickness is that I get sick in cars that are constantly jerking me about. You might not even be aware that you are jerking until you practice not jerking. Drive as though you have a fish bowl filled to the top, and you have to get somewhere with spilling any water. If you can master this -- and you are not already a master -- then your wife will be far more comfortable.