When you can hold your own in a conversation with a bird doing a fashion degree and chat shit about certain designers, silhouettes etc.
When you obsessively check your garms giving them a little 360 spin that you wore the night out for stains the second you wake up before having a cup of tea or a glass of water.
When you know postage prices and methods intimately.
When more clued up fashion mates ask you wear you bought some new gear from so they can swagger jack.
When you know your ginghams from your madrases, instant pattern recognition.