Some things about Shauri

[Bogertophis]

Your sling sounds like a fun idea for holding your snake so that she feels both safe & close enough to you to also stay warm. Love it!

I'd back off feeding any jumbo rats, as they tend to be very high fat & thus, less than healthy for a snake. They can & do die prematurely from "fatty liver disease". Your BP is only 4-5' long- for sake of comparison, the adult 7.5' BCI I used to have was only ever fed* medium rats (*except for one large rat, one time, that she was obviously less than comfortable with), and she was strong, healthy, not overweight, & lived a good long life after starting off as a very stressed rescue that came to me. In the wild, a snake would be better able to work off such a fatty meal, but then again, in the wild, few such opportunities ever present themselves, since life in the wild rarely allows either the prey or the predators to get to this point.

NOTE: As far as sizes of rodents fed, not all sources label them the same way, so actual weights are helpful- so we're talking about the same things.

And FYI, "power-feeding" tends to make a snake's body grow faster & proportionately more than the head (the bones are slower growing), so you get the opposite effect.
All things considered, I'm not surprised she is fasting, & it's probably for the best anyway.

Your tank is too small for a "5 foot" BP- a snake that's really that big should be in a 40 gal "breeder" tank at least, or other type of enclosure. If your BP really is 5', I'd say she's much older than 3-4 years as you were told...they just don't typically grow that big, that fast. Any enclosure for a snake needs to have a range of temps. for the snake to choose & "thermo-regulate" their own metabolism...in a smaller tank, that just becomes impossible to supply. They also NEED 2 hides, one on the cooler side, & one on the warmer side, because a snake will usually choose "security" (to hide) over the right temperature, so they won't be getting what they actually need...choices.

Exact temperatures are critical & all heat sources should be controlled by thermostat, & double checked with an accurate thermometer. You didn't mention the temps.? You want them to range from 78* cool side to 88-90* warmest part- this is essential to set up & monitor. Depending on how warm your room/house is, the UTH may not be enough to warm the air in the tank- or if it's running hot enough to warm the air, your snake will be at risk of being injured (burned) if she is in contact with the glass under the substrate for too long- & trust me, this happens way too often. Best prevented...vet care can be expensive, & burns can be severe, painful & even life-threatening (as w/ infections).

Hides- should be one doorway only, just big enough for the snake (with a meal) to fit thru. Most snakes prefer low "ceilings" that provide "back pressure" (a cozy feeling, safe from predators).
Here are some that many of us use: https://www.reptilebasics.com/hide-boxes Another reputable source of equipment is: https://www.beanfarm.com/collections/bedding-and-cage
Note, the "tree bark" tunnels are not "hides"...your snake may not feel secure enough to eat- but they make nice sturdy cage furniture in ADDITION to proper hides. Tree bark is also harder to sanitize after getting soiled.

If the temps. inside the tank need to be warmer, you can insulate the sides, back & even the bottom (except around the UTH), & this also gives more privacy that snakes appreciate.
Many augment UTH heat with overhead methods of heating, or use overhead heat devices exclusively. We don't all do exactly the same things, & some houses or rooms are colder to start with, so setting up a snake enclosure is always a custom job. Snakes (especially shyer ones like BPs) usually do better in rooms that are somewhat quiet, like a bedroom, but it depends on how active your household is too. I have snakes in most rooms of my house, but not bathrooms or kitchen. But I don't throw any parties either.

Glad to have you join us. I'll add more tips (or others will) when time permits. I can tell by your questions that you're a caring owner, & that's good to see.