I'm ecstatic to finally own a button-down blouse! I'd given up looking years ago, for all the obvious reasons ... well, you know. I'm happy to be a Front Room "Small". My dress size is 10 or 12. I'm an hourglass for sure, so can't say my boobs are my only "round" part, but my fit issues are ALWAYS the chest.
Your sizing chart on the web is bang-on: I measured myself before I went into Studio Intent and it said I was S, and the pieces I bought were indeed S. I don't know why women don't trust their measuring tapes. I think a lot of us get it in our heads that we're a certain size, and we won't consider anything else even when the evidence says otherwise.
LELAYNIA C - 32H