I like the idea and I can see it well enough, but reading it [though correct] sounds clumsy --- why? Look at the mixture of verb tenses in the first sentence: pound
ing/press
es/pois
ed 
Also -- being
uber picky here . . . although presumably it is a gun's trigger upon which she has her finger poised, the object of the sentence is the wall so it could be misread [by dorks, admittedly] as if the wall possesses some sort of trigger.
And -- cold wall, I'm thinking traditional brick/stone/plaster, yet it seems it must be metal, so I had to have an extra wee think there. So a couple of stumbles if your reader isn't sharp when they first come across this. And for more pickiness sake [and hailing the really dumb dorks; tired travellers between flights picking up a book for the second half of their trans-Atlantic journey] -- the phrasing of the second sentence could also be misread as the metal peels from her back as she pulls away.
Work this so the picture is absolutely clear and I think it's a goodie.
I am being deliberately picky of the phrasing, not you, Butterfly.
