Beccie, here's one way of looking at it without looking at who likes what body shape.
R32 GTR gives you Substance and Heritage
R33 GTR gives you Substance and more room in the back
R34 GTR gives you Substance and points for being more expensive
A blinged skyline gives you bling
Any normal skyline gives you a normal skyline
Unless your fellow year 10 friends (who I assume you want to impress) understand what a GTR is, then the Substance, Heritage and price is lost on them.
Most year 10 people and girls normally understand bling, it shines in your face. Get the skyline with the most bling you can find is my suggestion.
One suggestion, try to get in and out of your mums GTR rear seats, with your dress and high heels for the formal, with dignity or without exposing yourself. If you can't, may I suggest a 4 door car or the traditional chauffer driven limousine.