Hi Keaira,
Gorgeous dress. Love the style and colour. Although halter necks have never been a favourite of mine. Give me headaches.
As your transition proceeds, hopefully you will lose a little muscle mass on the top half of your body and your breast will grow a bit. Those changes should assist in developing the waistline Axelle eluded to.
A further trick you can perform with this style of dress to emphasis a waist line you may or may not have is. Wear a slip or petticoat underneath, preferably one with at least one layer of tulle, if not 2 or 3. If you know a dressmaker, or you could even do it yourself, stitch an extra layer of tulle round the waist line, about 8" long. this should push the skirt out, creating a false waist line.
Pity to waste such a lovely outfit. You'd look lovely in it. In the meantime, be safe, well and happy
Lotsa huggs
Catherine