All-wheel drive is by far the best solution, with 4 studless ice tires such as a Nokian Hakkapalleda (sp?), Dunlop Graspic, mostly anything IMO other than a Blizzak. Blizzaks are good new, but when you get to the 60% point you're on summer rubber, so you need to keep new ones on, the other (better IMO) tires I mentioned have winter compound down to the cords (the reason that Jonathan is having trouble with his car and used Blizzaks).
If you have to choose 2WD, I will take RWD over FWD anytime, I've been driving in snow for over 30years, mostly aggressively and I have never stayed home due to weather (drive 1500miles/week in Michigan) and it plain works. With RWD you can put a 50# bag or two in the front of the trunk, sand is good as it can be used for traction, a bag of salt or better still is Calcium Chloride (melts ice when it's REALLY cold). Keep it dry.
Look on ebay for a set of Shru Grip Z cable chains in her size, or buy new from SCC (the manufacturer) and show her how to install them, I've been in places where two 6X6 F350s were towed up the dune and I drove out with my chains on regular M&S tires, worth the expense for a set (I carry 4).
