Have you kept a log of actual feeding dates and what size feeder she ate? I have one BP that will be two this summer and currently weighs about 600 grams. Her body shape is fine, but she only takes a feeder every 3-4 weeks.
Have you tried supplementing her with NutriBAC to give her gut flora a boost?
Also... this is pretty gross... but have you noticed any undigested matter such as hair or bits of bone in her stool?