This is what I'm curious about. He was part of her body, just as our bodies are part of our parents bodies. If His body is real and true in that wafer, then her presence is in that Eucharist. And when that wafer is changed into His body, her presence is in that wafer too. One-half of the substance of His body; half from the Holy Spirit and half from Mary.
My question is, does the Catholic Church teach its members this, or is this just something that isn't considered by Catholics who believe that Christ is real and present in the Eucharist?
I am no theologian, and perhaps some other FReeper could answer it better.
But we believe the Eucharist is body, blood, soul, and divinity of Christ. Mary had her own soul, so unless we are willing to postulate two souls in it, then no, the Eucharist is not Mary the same way that it is Christ. Also, we adore the Eucharist as God, and Mary is a creature without any divinity whatsoever. If she were in it, we would be guilty of idolatry.
However, I have heard expounded, and the article above touches on it as well, the connection between Mary's body and the body of Christ. He owes His body to her Fiat in a crucial way--there is certainly some mystical connection there, though what it is I can't even begin to say.
Our bodies aren't "part of our parents bodies," though. They have their origin from and in our parents' bodies, but they aren't part of them. My son's body is not part of my body; it's a whole body similar to my own (but younger and better-looking).
Christ's human soul did not originate in Mary, because it is Catholic dogma that human souls are directly created by God. (Some Protestants hold to a doctrine called "traducianism," which says that souls are derived from one's parents in somewhat the same way our bodies are. That belief is heretical for Catholics.)
Christ's divinity certainly did not originate in Mary, because it pre-existed her, and also, of course, "you can't give what you don't have," and Mary has no divinity to give.
By analogy, if you sent me a lock of your hair in an envelope, is your mother present in the envelope? (The analogy is imperfect, because every particle of the Eucharist is the whole Christ, while the lock of hair is only a part of you, but still ...)