492 The Father blessed Mary more than any other created person "in Christ with every spiritual blessing in the heavenly places" and chose her "in Christ before the foundation of the world, to be holy and blameless before him in love".137 [Cf. Eph 1:3-4]
See anything wrong with that statement? Let's compare it to the wording of their prooftext:
3 Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, 4 even as he chose us in him before the foundation of the world, that we should be holy and blameless before him (Eph 1:3-4).
Eph 1:3-4 doesn't single out Mary as the object of Eph 1:3-4, but Christians in general. The elect.
Indeed, it says absolutely nothing about Mary. At best, she would be included among other Christians.
Ever since Newman, Catholics appeal to the theory of development. Here we see a passage of Scripture decoupled from its context, to prop up Marian dogma. Once Scripture is decoupled from context, the process takes on a life of its own.
There's nothing intrinsically wrong with theological development, but it has to be logically valid. Problem is, Catholic theology develops in the same way a seminal fictional motif develops over time. Take the literary evolution of the Faust legend or the Arthurian legend, or the cinematic evolution of Batman, Superman, the vampire mythos, or the permutations of the Star Trek canon. Because fiction isn't subject to factual constraints, it can change. The only limit is consistency and is the imagination of the storyteller.
But historical events can't change. They are what they were. Frozen in time.
Catholic theology undergoes the kind of legendary embellishment that's characteristic of fiction. Uncontrolled development, because reality poses no check on where it can go.