Famed restaurant critic Gael Greene wanted singer Roberta Flack to attend her annual Citymeals Power Lunch for Women for years, and she’s finally getting her wish. “In the 1970s, I listened to her song, ‘Killing Me Softly,’ ” says Greene, whose 26th annual Citymeals lunch is tomorrow at The Plaza, reports The Post’s Jennifer Gould Keil.“It was so haunting that I put those words on the first page of my book. Now she’s coming to the Power Lunch. For us, it’s a great triumph.” Flack was invited this year by her goddaughter, Tren’ness Woods Black, who’s also the granddaughter of late Harlem restaurateur Sylvia Woods.