Antique romper from PLT

Super flowy, the chest area is revealing but I would take a pin or a double sided tape to close it a bit more. It fits true to size (US 10) , I’m usually 14-16 in US but I forgot I that I purchased it in the Uk size. But I only wore it once, my torso is too long for it which is weird because I’m 4’11 but I believe it’s just the size, how can I go from a 14-16 to a 10.