Damn! Can imagine Amber saying "Penny for your thoughts bitch!" Or if she has a dime "Gail, your a dime a dozen!" Hmmmm, well enough of this non-cents, hopefully Gail knows how to 'change' the situation into her favor.
money from on high
actually, no, if you drop a penny from really high up it won't kill someone, if i remember rightly. hurt a lot though. maybe do some shock damage... but it's too light. it's penetration sucks.
to puncture something (armour, skin, bones such as the skull, etc) you need mass as well as speed.
the road shouldn't crack there either, i believe, but either way, that coin should have Bounced and been heading right back up again, not stuck there.
of course, who cares about real physics in a superhero(villain?) comic? :D (though that implied power in the 'you've got to be tough enough for your own strength not to kill you' bit is a nod in that general direction)
admittedly, I'm a bit late to the party on this one and didn't read the whole comment thread, but whatever :D
Getting reality in your fiction
Terminal velocity of a quarter is only about 28 MPH; but even if you shot someone with a coin at 700 MPH, it would only sting a lot and maybe bruise, because of the low mass and shape. Mythbusters did an episode about it.