I have a hunch that what you're smelling is her musk, & that it's not actually from her having slid thru fecal material, as that washes off easily. It's easy to
forget that boas that are very stressed can musk, as they aren't "known" for doing so as some other snakes are. One of the worst smells I've ever had was
the musk from my baby rosy boas when I had to sex them... So I feel for ya. Musk lasts longer than fecal odors.
The only other thing I can think of that could smell bad & continue to do so is infection (necrotic tissue): hopefully that's NOT your problem & that you've
thoroughly examined the snake? You really need to determine what the odor is. (have fun!)
Very good point, I hadn't thought of that. If it was a King, milk or corn that would have been my first thought, I bet.