Ok, an unpopular view here, as possibly not politically correct, but from a practical viewpoint.
Its a lovely dress but it will bring her lots of attention due to its va voom style and how she will look in it tbh.
Is yr daughter confident, able to laugh off comments made, unwanted attention etc? if so, let her go ahead, if not, she'll possibly feel exposed and vulnerable.
15 is a difficult age and most girls are learning how to handle attention, welcome or not
Prepare her by having couple of put downs ready ensuring she's armed znd dangerous :). My niece's personal devouring was "dont sexualise me" in withering tones...
Otherwise, I'd suggest she put it away and waits a few years.