Amy Robach was forced to defend herself after she was told to "act her age" by a nasty troll on Instagram.The Good Morning America host, 48, won huge support from her fans after she revealed the negative comment she received.MORE: Amy Robach's fans can't get over her beautiful bikini selfieAmy gave the perfect response to her naysayer, sharing a gorgeous photo of herself flashing plenty of leg in a stunning yellow floral wrap dress by Alivia.WATCH: Amy Robach's five style lessons"I had to laugh