I'd get them off the walnut shells. I'd also consider giving them a bigger water bowl.

I have a 55 gallon display cage in my living room where I keep one of every KSB morph I own 'for the kids'. We use a mesh top and lights and we use hardened burrowing sand with structure like aquarium logs and plants for them to hide in. I have increased the size of the water bowl to about half the diameter of the longest snake. They soak a bit more than the ones in sterilite but they all for the most part have good sheds.

As far as the pacing goes. I find that mine pace when hungry or not able to find enough heat or cool areas. When I see them pacing I first check the tank and make sure the warm side is the temp I want it and the cool side is cool. If both of those are ok it normally turns out they are ready to eat. But they are captive so maybe your girl has seen Braveheart one too many times? How often do you feed her? How old is she? What does she weight?

Below:
Voted most likely to escape at our 2009 Kenyan Family Christmas Party!

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Mark Huntley
Sand Boa Morphs

Kenyan Sand Boa's
4.1 Rufescens
1.2 Albinos
0.5 Dodoma
2.1 Flame
2.5.8 Normal (orange)
3.4.10 Anery
0.1 Snow
2.2 Hopeful Yellow Snow
0.1 Splash Albino
1.0 Splash Anery
1.0 Orange Stripe 100% Het Anery
1.0 High Orange Stripe
1.0 Yellow Stripe
0.4 High Orange Tiger
2.2 High Orange
2.3 Boston Terriers
0.2 Sooners
8.30 Rhode Island Reds
0.0.15 Tropical Fish
0.1 Moody Wives
1.1 On the fence in-laws
2.1 Rug Rats

http://sandboamorphs.blogspot.com/