I believe it's not so much what you look like but rather how you interact with others. If you're loud, stuck up, a little too confident for a girl, and walk around like you're Paris Hilton or something you'll appear to be a high maintenance girl. Personality conveys 80% of who you are, the way you dress conveys only 20%.
Whether they know you or not makes no difference, this is how you project yourself towards people.
For most people there's a fine line between being vain, caring about your appearance, an being high maintenance, maybe if you could develop on your average appearance/wardrobe then we could give a more accurate analysis.
However, it's nt necessarily how one looks, it's how one acts.
If her hair is always perfect, if she wreaks of perfume, lots of eyeliner and eye shadow, lip stick, shiny necklaces, rings, bracelets, perfectly painted nails (if they're multicolored or have designs you're super high maintenance), and shoes that click when you walk to draw attention to yourself.
The funny part is that a girl like that is really attractive to me but I would never approach her because I would assume I could never keep her happy.
For me stuck up and high maintenance are different. I get called high maintenance all the time by my friends and family because I always wear makeup no matter where I'm going and use a lot of hair products stuff like that. and for me stuck up just means bitch.