Dear Amanda,
I perhaps wouldn't choose a blazer so much ... it's not in line with the lovely, floaty nature of your frock and may not be the best shape. The black in particular looks extremely heavy and drags your entire look down. Rather, I would have worn a fake fur, cropped coat in a light brown or cream, and definitely have taken it off for the stroll down the red carpet (note: to real folks that means for your entrance into the party). A mauve dress like this is extremely hard to make work with such a structured jacket.
Yours in style always,
Nedahl xx