Hi Keaira,
For my money, I'd keep the dress, loose weight and use the dress as reward for being so clever. An Aussie diet that I have used and seen many others use successfully is based on 70% what you eat, 20% modest exercise and 10% workout exercise.
The diet bit mainly suggests you drop the carbs, sugars and Fats (of course) and go for proteins with plenty of vegs. I dropped 16kgs in 6 months, and I've kept it off. I'm now down to a size 12 in skirts and 14 in tops. VAST improvement from my 14/16 resp. 6 months ago.
The good thing is the way your dress fits at the moment, it won't take long at all for you to lose it. Nice dress.
Be safe, well and happy
Lotsa huggs
Catherine