How can I look older?

Okay so before everyone starts moaning at me don't bother I realise one day I'll be thankful for looking younger than I am but right now it's getting me down. I'm 21 but I get mistaken for 14-16 by the majority of people which doesn't bother me to much in general day to day life. But when I'm on a night out and a friend will have a guy talking to her who's her age or older whereas I get lads who ask me what high school I go to and wether we could be in the same year and whether I'd 'kiss there best mate'! VOM. It's just down right frustrating. I'm only 5ft 2 that doesn't help because even with heels on I'm smaller than everyone. I go out in clothes suitable for my age and I avoid pastel colours or my hair up because it makes me look younger. Is there anything else I can do?!