Alex- my experience is very similar to yours.
I switched my Female BP to frozen at 13-14 years of age. One medium or even a large rat will/would not satisfy her. She would stay in food mode for 2-3 days and be very cage aggressive. She would take four mediums and I stopped there. But she would still be in feed mode for a few days.
To mellowed her out I have to feed her a very large rat or jumbo once a month. Then I didn't have any cage aggression anymore.
She does go on winter fast each year and to reiterate, she gets fed monthly when not fasting.
I know the guidelines and many folks here say to max out at medium rats. But those are guidelines and guidelines always need to be flexible. Not every BP acts and or reacts the same.
Elvira, normal