I use Muck Arctic Pro boots 1 size larger than my normal boot size. I wear 1 pair of darn tough mountaineering extra cushion over the calf socks. Feet never get cold and I ice fish almost every day.

You can try boot warmer (blanket) insulators that zip over a hiking boot. A thin pair of polypropylene liner socks (underneath a pair of winter socks) will help wick moisture away from your feet. Wearing pantyhose will help thwart off the cold.

Try to stay well fed out in the cold. Eat something like a candy bar before you get cold. Once you get cold...it's usually too late to eat something to keep warm.

Try tightening and relaxing each muscle in your body. Start by wiggling your toes...and then proceed upwards in your body.

My main remedy for cold toes: Is just getting up and walking around.

Be aware of frostbite and the signs. Don't ever let your toes freeze-up like hard rock candy.

there are different ways to keep feet warm doing different things
till the OP, tells us HOW and when his wife wants her feet warm , all were doing is guessing at when and what will work

I doubt she needs heavy boot blankets or heat packs sitting on the couch, and they also don'
t work when walking far, as your feet are already making heat from walking!
there are lots of great ways to HELP keep feet from getting cold, but they all work, based on what activity your doing
and pending what activity your doing, using the wrong way can make matters worse NOT better

It is important to keep your head warm. Because if it isn't...blood will rush from the extremities to the brain, in order to keep the mind functioning properly.