Elements in the Human BodyWe have more calcium in our bodies than any other metals combined, so giving a generous percentage we are still under 2.5% (1/40) metal. We never see any alkali (or alkaline earth) metals being pushed that I can remember in the books, so I'd assume that they're not included in pushing or pulling. If they were, Vin (or TLR, for that matter) would be burning duralumin to pull vital bones from peoples' bodies on a regular basis.
I just reread the battle and its never said that she couldn't move her arms, etc. Only that it felt like the metal in her stomach was going to be ripped out. I think think its a moot point though. Elantrians don't have red blood, which means there is no iron in their blood.
Whether or not the Elantrians have no iron in their blood is a non-issue. There are only 3-4 grams in the average adult body at any given time, which is a very small amount. If TLR pushed Vin using the iron and copper that was in her body naturally, he'd be pushing less than a half of a percent of her body weight. Even with duralumin and his Feruchemical tricks, I don't see this being a viable combat technique in any situation. If anything, he'd end up blasting all of the Allomantically active metals out of his opponent's body. Painful, but not an instagib for most of these characters. If the metals, against all odds, stay in their body, think of the resistance of a very light breeze.
Speaking of instagib, in the Unreal series teleporters can be used to kill people, which makes me wonder about Elantrians' capability in this regard....