Apart from stupid women i would have told her to sit down and shut up.
I don't care about your outrage, complain on twitter or to hq after the flight etc, not delay others when you've the option to cover up.
There's a dress code for a reason, to prevent people from wearing seriously offensive or revealing things.
It's to stop people wearing swastikas etc, or should there be no dress code and men be able to wear tops with fully nude women on?