First thing I would say is to recheck the sex. Plenty of times Male Ball pythons will reach their "happy" weight, and call it quits. I have a 4 year old Spider male that weighs about 750 grams, and only eats 4-5 times a year. He breeds like a champ, and I guess he is at his mature weight, and doesn't feel the need to get any bigger. If it is indeed a female, then my first suggestion would be to offer food a bit less frequently. It sounds from your original post like you are trying to feed every 4 or 5 days. I would back off to a 10 day feeding schedule until you get her back to eating regularly.

Just my .02,