Preening is more of an animal/natural instinct so unless she is LOOKING at you/TALKING TO you then it's not an IOI. It's just her being a woman in society!
But, on to your approach/open issue...You could have just said "How rude!" just like you did in your post and then follow up with "Usually sociable people do that kind of thing at home!" as a C&F line.
Also, (and I just thought of this one because of your question so I want to go try it immediately!) you could go with a bit more playful attitude and say "Don't act like you're not enjoying this elevator music...You know you love it!" If there is no music playing (sad

) then you could say something along the lines of "This elevator is so bland without music, They need to be playing some Sinatra or something because I am just too awake right now!" (that is unless you dig elevator music...hey, some people find it relaxing

) OR you could go with the Shit test/Cocky/Funny/Serious tone line and straight up say "Hm, There's no music in this elevator...You better start singing right now missy!"
Btw, I love your Olympic-Fucking-Seconds bit. LOL. This is a good thing to keep in mind because on an elevator you have even LESS TIME FOR THE 3 SECOND RULE! Think about it...You don't have to make the physical trip over to her to approach because she's already right there! Open her ASAP!
Hey man, the true MPUA claims to be able to pick up anywhere so you might have to revamp this one into an "Elevator Game" Series haha!!!
