Short hair doesn't make everyone look older and Natalie Portman made an adorable pixie, but when the hair is at an odd growing out stage (Portman had famously shaved her head the year before), you don't want to pair the whole look with a frumpy shirt. The color washes out Portman's pale skin and just makes her appear ... blah and a few years older than she is.
Also see: 25 Makeup Tips for Older Women