I'd choose short front and long at the back (I am the same, about 5"2 and 100-110lb)
Try to wear some nice jewellery, I like something simple, classic, elegant and also something "POP!" "wow" factor is very important!
Something like these, I borrow them from my sister all the time, she has nice stuffs and we like "western style" (they are from PINK Espresso if you need more info, PM me)
Have fun at your prom