Angie, I just wanted to say I found it helpful that you sometimes fit women in jackets that won't quite button over their chests, but fit elsewhere, and that it's okay to buy a jacket that is meant to always be unbuttoned.
This is common theme for me. I'll take an hour in the dressing room going back and forth back and forth between two sizes, not sure which to go with.... always thinking "well it should be buttonable... but the smaller one makes me look slimmer unbuttoned and fits better in the shoulders and length... the larger one buttons but the lengthwise proportions are all wrong." (This is particularly true when it is not petite sizing).
... and I analyze whether the buttons can be moved just a smidge. I know the button holes can't be moved... but sometimes that's all I need... to have the buttons moved to give me just a pinch more space in the midsection/chest.
What I like about the style of Nicole's jacket (other than the ribbon detailing - very nice!) is the three buttons being so close together (defines her waist), and the placement of the pockets. Perhaps if they were slightly slanted they'd give even more waist definition (tip from your recent blog). The top button looks like it is in the perfect place to "lock and load" her chest, if she wants to do that.
So Nicole if you do try on the smaller size .... and it fits better in the shoulders and sleeves etc... but you still want something that can be buttoned since you're thinking of this as an outdoor blazer... check to see how much room there is to move the buttons closer to the edge. That's the simplest thing in the world to do.