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