No VegasDev. If Vin's mom was controlled by anything, it's Ruin. You know why? Ruin wants to keep Vin alive. Ruin chose Vin to be the false Hero of Ages so she could release Ruin.
And I'll give you citations!
p. 417 - This page (Well of Ascension, of course) is where she tells Elend where she got her earring. She describes that her mother heard voices. Her mother killed her sister, but then gave Vin the earring. Vin says, "As if... as if choosing me over my sister. A punishment for one, a twisted present for another." If we link Ruin to this, then it's obvious that Ruin, at a very early time, decided Vin was the one he wanted.
And so, like any ultra-manipulative uber-spirit locked away for a millennium, he began to spend his time manipulate things to bring Vin to the Well of Ascension.
p. 453 - Zane's death scene. Zane thought that Vin would save him because she was the only one the voice (God) didn't want to kill. The minute Zane thought this, God whispered "Of course I don't want you to kill her." Then, in a twist of fate, God says that Zane was never insane.
This tells us some very interesting things. Obviously, the "God" is Ruin, this has already been mentioned several times in the forum, so that shouldn't be a surprise. But the interesting thing is that Ruin wants to destroy everything. Zane is told to kill everything, all the time. No exceptions. Except for Vin. Why Vin? Because Ruin wants Vin to release him at the Well of Ascension.
Back to Hemalurgy, I think we can say Hemalurgy is the "art of wielding the metals inside your body". Loose definition, yes, but it's something to go on.