Ahh, the three of us meet again! This time I'll be third party. -puts on bulletproof vest-
While I agree that the internet is a tough place to get honest to goodness facts off, and there's a LOT of bad info out there, they said that one of the most "reported" illnesses is RI's. Which means that other people are claiming it as a common problem. So by that logic, I'm gonna say that they're going off of OTHER people's experiences, which is what the OP is/would be doing anyway. So without Burm owners/specialists chiming in to say otherwise that's about the best any of us can do.
To the OP, I'm no Burm owner, so I can't offer anything helpful in specifics about your new girl. I'll just say that I held a 9-footer at a show and she was like three times as big around as your new one. But being skinny isn't anything that good meals won't fix. Start slow with maybe one or two jumbo rats, and work up from there?