Questions about a soaking BP

[Bogertophis]

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I would have to call my vet to get her weight as I don't have a scale. The only other option I have at this point is driving I think four hours to another reptile vet that I have never seen before.

Accurate digital scales for home use are fairly reasonable these days, thanks to large office suppliers like Staples. It might be helpful for you to pick one up, since your snake has long-term health issues- you want to know if they're losing weight, without the stress & travel to the vet. And it will help them correctly advise you about when or if you need to bring the snake in.

To weigh a snake is easy: they need to be in a small container (plastic with ventilated top, cardboard box, or small cloth snake-bag) that sits on the scale. You get the weight of the contained snake, then weigh the container by itself & subtract that weight from the combined weight to get the weight of the snake.

Have you considered keeping her on paper towels as substrate & just giving her a high-humidity "hide" (in addition to the warm & cool hides)?