By Liam Buckler Tributes have been paid to a US Army soldier who tragically died by suicide just days after her daughter’s 12th birthday. Staff Sergeant Michelle Young, 34, served two tours in Afghanistan and was a much-loved fitness and fashion Instagram influencer in her spare time, according to her friends. The mum-of-one, who had served in the army for 16 years, had just shared a post celebrating her daughter Gracie’s 12th birthday to her 100,000 followers days earlier. “Happy birthday to the sweetest girl I’ve ever known,’ Young wrote. “She’s a force to be reckoned with, she’s witty, ambi…