You can put me on the list of people who will never buy from RodentPro again. I've tried most of the big suppliers and they are one of the few that earned a spot on my 'oh hell no' list. Layne Labs is my own go-to but there are other good suppliers out there as well.
Re: your beautiful Boelen's: I believe you when you say something seems wrong. You know your snake. We have so little reliable info on the lifespans of various species under captive management, but the one thing that has been a constant across species is the ever-increasing evidence that snakes in general can live 20-30 years or more if provided with good living conditions. So I'd be really hesitant to categorize 11 years as an old snake.
It's at least a relief that her bloodwork values are normal. I didn't see any mention of radiographs being taken to see if there are any masses that might indicate growths/tumors. I realize that's a crude way to assess the possibility, but given what you describe as well as normal bloodwork, I'd at least want a preliminary look at X-rays.