A. You can share to social from the Response page. Head to response, click the arrow to the right of the mailing and choose "share on social". Now, there is currently a bug in our Social connection that is not allowing you to change your settings from the Response page. But it will allow you to send to the most recent page that you've shared on.
B. Alternatively, you can open up the response data for that mailing, click "open webview in new window" . When the window opens, you can grab that URL and share that on to social media as well.