you can either collect dry dirt from outside, or go to a garden store and get plain top soil (no fertilizers) and use that or get some construction sand (play sand is to fine and can cause crop impaction) and they can dust bathe in any of those. they will love it.
yea I have never seen that before, does she walk normal other times, or is that all she is doing to get around? does she only do that on carpet or does she do it on shavings, grass, hardwood, dirt? it could still be dust bathing behavior, just doing it in a odd and cute way.
she could be trying to dust bathe, if you could take a video and upload it to Youtube and post it here you might be able to get a more accurate answer.