Nerida,
Very interesting about your friend going to Royal Ascot! Yes, I feel the Majorica brand pearls are often used by wealthy women who prefer not to travel with their "real" pieces. They have their designers make copies using CZ and the Majorica pearls. The imitation pearls coming out of China are not near the quality of the actual Majorica branded pearls.
Fine Jewelry at Nordstrom (mid 90's) carried some basic strands and earrings when I worked there and still does; I often admired them, because they were large, which I am drawn to, but I could never decide what color to purchase, gray, deep cream, white? The cream was much like pale golden SS. (At that time Miki's were Nordstrom's premier line, didn't buy them either, but did win a pair of studs.)
When initially sold, it's clear these are imitation pearls, however on the secondary market is when the problem begins, or that Grandma has treasured and referred to them as "her pearls" for so long.