If your wife has a blood clot or you supect it, then a medical exam is in order. You can't guess that kind of thing!
I've had leg cramps for years - it can be agony. A spoonful of magnesium powder (dissolve in water) works well, usually within a few seconds. I've used a couple of different brands and don't know what's available in US but when you get a powder or pills, get the highesdt mg content of magnesium you can, and prefereably buy a practitioner-level powder. I have used a basic health-food store brand and it's worked too, but it's nice to get the best.Definitely one for the medicine bag.
Our respective reasons for getting cramps may differ - however, magnesium is well-known for alleviating cramps and in fact I found it useful (in an emergency) helped to stop the tightness in my chest during an asthma attack. I also found that breathing REALLY deep and stretching aided a bit until I could get to the bathroom where my powder/pills were!