The word doesn't carry much connotation, maybe something like "that person cares about looks". What I mean is it doesn't carry any double meaning, it is very strictly related to appearance only, maybe a little bit about being self-important/self-obsessed?
I'm relatively sure you could use it like this in a sentence "She got boob implants, she's so ____"
The word is not vain, narcissistic, superficial, conceited, snobby, cosmetic, shallow, flamboyant, ostentatious, classy, exhibitionistic, gay, extravagant.
It's not a very complicated word, probably 6-10 letters.
The definition would be something like "To do with (outward/physical) appearance".