15-20% of body weight for juveniles/growing snakes - most people don't feed a 3,000 gram snake 300 grams of rat (for instance).
Trust me, they stretch a lot. 200-220 is about an average sized adult mouse or rat pup and she should have no problem with that. They basically have an elastic bag hanging off their spine for for a throat. *Don't* measure her prey by her neck, but by the bulk of her body/the widest part of it. BP are REALLY stretchy - even more so than some other snakes - and can take some big meals without trouble.
I keep this around for demonstration purposes:
This was when my BP was about 400 grams. That's a 20-something gram mouse. It's WAY too small for her.
This is about right - and in truth he could have handled bigger.
No problems at all. Seriously. They stretch.
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