Do-it-yourself maven Barbara K. pushed off surgery to make her holiday event at Macy’s last week. Just 12 hours after leaving the hospital with an injured back and walking with a cane, The Post’s home columnist put on a smiling face and gave a two-hour holiday DIY demo at Macy’s — where her new DIYVA tool and accessory line’s sold. Barbara, along with former “Real Housewives of New York” star Kelly Bensimon, demonstrated how to install curtains and a mantle for Christmas stockings, as well as how to decorate for the holidays for under $100. But trouper Barbara was in such pain following the event, we’re told she scheduled back surgery this week and is recovering.