Weird. I'm no expert by a long shot, but I wouldn't think burns would cause stunted growth. Do you have a picture you can post of her to show body condition?

If a boa is in correct condition, it will have the shape of a loaf of bread. More square than a BP, but no emaciated. Also, were there any other symptoms... any stuck shed, dehydration, etc.?

For a boa that is 2 years old, I feed every 10 days - every-other-week. The prey item should be the girth of the boa and either leave a very small or no lump. BCCs do grow more slowly than BCI (I only have BCI and BCA) but I do know you are not supposed to feed multiple prey items.

I'd think try a large mouse or rat pup that is of appropriate size every-other-week and see how it goes. Hopefully someone with more BCC experience will see this and post though.

Good luck!