Could she have fluid in her feet? Maybe from some kind of venous insufficiency (? not from medical knowledge, more from things I've heard said about me when trying to find a cause). I find that certain things can aggravate it for me, such as heat, flying, not moving and sometimes when I am lying flat/flatish have my legs up otherwise.
If they are going numb and if something like fluid is masking things, such as feeling shoes pressing/rubbing that could leave her more at risk of damage.
I find keeping them cool is key, using cold water, gels/sprays and dangling them out of the bed, off the sofa can help me. The swelling is more obvious in my feet (though I have rheumatoid arthritis as well) but the fluid is more obvious in my legs, if that makes sense, I have to watch as they dent and bruise very easily and I don't always feel things sticking into them, especially when they are feeling numb and with pins & needles and such.