I wouldn't breed her. 900 grams is really small to be breeding in my opinion. I am far from an expert, but I believe most of the individuals who have mentioned breeding a female in that size range have done it only after they are sure the female is fully mature and just happen to be a smaller female. Given how recently you acquired the animal, how much she has grown, and how small she still is, I would definitely wait. Think about how much extra weight she could put on in a whole year. If she were just a small female I don't thinks she would be gaining that fast. She is probably a late 07 who has been fed a maintenance diet by her first home/breeder, so she likely needs more time to grow. Just my opinion, take it with a grain of salt.