I'm sorry you didn't get the Motobecane. It looks a lot like Mom's Motobecane Grand Jubilee, with the same Vitus tubing, as well as the single top tube that splits part way.
I did pick up a Grand Touring, which wasn't quite as nicely finished as the Grand Jubilee. Also, the Grand Jubilee uses 27x1 tires/wheels, while the Grand touring had 27x1 1/4.
Anyway, for a women's bike of the era, the Grand Jubilee was a great bike.
I know she did take it touring a bit in the past, but probably not with a heavy load. I do know the flexy feeling with touring on my vintage road bike. Perhaps I should try a LHT or similar someday.
It might depend a bit on how much of a load your GF is planning to carry. She might not notice any flex if weights are kept below 30 pounds or so.