For an adult that size a good rule to follow is to only feed after they poo and after they shed. This usually boils down to about twice a month or once every 3 weeks depending. I also don't feed mine very fat rats. I choose the large rats that look more lean than the others when I am euthanizing to freeze for her since boas can't process fats like pythons can.

I've been in a money crunch lately but I'm planning on ordering a box of quail so I can supplement her with birds as well. They are more lean and boas eat a lot of birds in the wild so I figure it's a healthier way to go.