Looked at pic and saw updates to thread. She looks good to me.
I agree with what's been said and my initial thought.
Small rats should be fine, but I would offer every 2 weeks. I would plan to stay on small rats indefinitely - unless she gets huge and/or starts losing weight on small rats - very unlikely.
I feed Shayna, my 8 year old, 2kg, female BP, a small F/T rat every 2 weeks and she eats like clockwork except during her 4-5 month winter fast (which is totally normal for many BP's). When I offered her mediums, she would often skip meals and and wasn't as enthusiastic an eater. With the small rats every two weeks, she went from 1.7kg to 2kg in two years and pounds her food.
I tell many people how efficient BP's, and really snakes in general, are. Less is usually more. Remember, a captive BP probably is more sedentary then a wild BP, and in the wild BP's primary prey is African Soft Fur Rats (ASF Rats). An adult ASF rat is about the size of a small rat you would get from any reputable rodent supplier (60-90G).
Good luck and keep us posted.