Wireless headphones have their own amp and volume control built into them. Problem will be that many TVs won't let you use the internal speakers at the same time you use the optical audio output or built in bluetooth. The solution is to connect one of these to the optical audio output of the TV http/www.avantree.com/long-range-bluetooth-transmitter-and-receiver-avantree-oasis-plus.html
Connect a soundbar to its' optical audio output and pair headphones with it. Now you can adjust your volume with the soundbar remote and your wife can independently adjust the volume of her headphones.
Check the TV manual on how to turn on and configure the optical output. You will have to set it to PCM.