Few cars are equipped with jacks that will stand well in such soil.
The days of the jack with the large base that works in anything but
quicksand are all but gone. Smaller jacks save space as well as being
lighter. Besides, flats are so much more rare now than back in the..
let's just say back then.

A 12"x12" piece of diamond plate aluminum would serve well.

Back in about 1965 or '66 Dad and I were out somewhere in Palmdale-
back when there wasn't a freeway out there. In the old '57 or 58(?)
Ford ranch wagon- the one with the REAL wood siding applied over the
metal. Got a flat at about 10:00 at night in the desert. He pulled as
far off the road as he could, but it was all sand. Believe it or not,
about ten fewwt from teh car was a discarded real estate sign-
masonite I believe. I was enough to sturdy the jack. Still remember
watching the car sway a bit everytime a semi passed by.

Instead of a better jack, get your daughter a cell phone and
membership in the auto club- you'll both sleep better.
       __  __
Randy & \ \/ /alerie's
        \__/olvo
   '93 960 Estate

I've always carried a piece of plywood about 6" x 8" in my cars just for
this purpose.  It's something my father impressed upon me, maybe because
he learned this lesson the hard way.  The old "post" type Volvo jacks I
grew up with were very poor in this design aspect as well.