Hello
2 weeks is a very short time to lose considerably.
Get your BMI estimated after measuring your height and weight. Try to achieve a BMI less than 25 with regular cardio.
You can lose 2-3 kgs in 2 weeks time in a healthy way.
I would suggest you to avoid fast foods, junk foods, fried foods and desserts such as sweets, chocolates and ice creams.
Start different forms of cardio such as running, jogging, skipping, swimming, cycling etc to get back into shape. Start with 1 hour regularly to lose at least 500 calories regularly.
Take care!
A seamstress can fix that with no problem. It won't cost a fortune. Take it to a private seamstress that is not affiliated with an expensive store if you are worried about money, and get an estimate. Don't hurt yourself. Don't stress yourself. Just fix the dress. Congratulations, by the way. Relax and don't make things harder than they have to be.