a lot of it is genetics and gender. you can't spot reduce so you can do all the cardio and crunches you want, but chances are it will still be their. take a good look at your siblings and parents and if they carry their weight in their mid section chances are you will too. check your diet and get rid of all the booze your drinking that's just empty calories and carbohydrates. if you want to get rid of back fat/love handles you need to reduce your all body fat, but again you may still have fat their. don't skip meals your body will go into starvation mode.
does the back fat come out because the dress is tight or because of the bra.. if its because of the bra you can put a ponytail/elastic in the claws and then cut it and tie it after you past it through the hoops and that makes the back fat stay in its place and if its because of the dress work out
PLANKS GIRL!!! Spiderman planks Superman planks and just plain planks. build up your time start with 30 seconds and try to go for longer the next time. Or if you're doing reps start with 15 and work your way to 30 on each side. Also rowing is really good for sculpting the back.