Well i don't know about a "Lady" fruit miroir, but I can tell you what a Fruit Miroir cake (french, actually) is.
You start with a base of a round of sponge (usually genoise) and that is surrounded by thin layers of almond biscuit layered with jam in a striped pattern (this is usually built in a cake ring/mold). A fruit mousse is then prepared and the ring is filled to JUST below the top and frozen. The top is then given a slick fruit glaze (usually apricot nappage blended with whatever fruit puree was use to make the mousse). The classic flavor for a miroir cake is cassis (black currant), but I made a peach miroir as part of my culinary school final exam that would knock your socks off. If you want the recipe, let me know and I'll PM you when I get home!
The only other possibility I know of is that maybe it is referring to a type of glaze that is also known as "miroir" for similar types of cakes, but I've never used such a product, so I don't know anything about it.
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