There is no minimum weight written in stone, 1200 grams is simply the most widely accepted minimum weight for female. Remember, females can breed at lower weights, however you increase your chances of slugs, smaller clutches and even ending up with an egg bound female. It's best to follow the best practices and breed females with enough size to support eggs, some clutches can weigh as much as 600+ grams can your female afford to loose that much weight?

I would say take your time and get her up to weight, you can try early next "season".