I found this adorable vintage 1959 shirtwaist dress pattern, at a thirft store: McCalls 4948

And the size looked exactly right, from the measurements listed. I started a muslin, because these vintage patterns are always tricky size-wise.

I altered the pattern because the original has TWO zippers! WHY? I eliminated the front zipper thinking buttons would be much cuter and easier, and got rid of the side zipper by using elastic to gather the sides instead of sewing them permanently. Tada, it's now a super easy pull-on dress!

But... When I put it on it is huge in the bust and not anywhere near as cute as the picture. It easily fits onto my G-cup dress dummy, and I'm only an A-cup!

I'm pretty good at sizing up and down when everything doesn't fit, or in the waist, but this is mostly in the bust and the shape is tricky because of the collar.
Can anyone help me with how to alter this so it fits better?