Another possiblity is she just wants to dig a burrow. If you can provide enough "hide boxes" for one who only wants to dig then they often will stop that.
Ours has never been a digger because one of the first things I read when we first adopted her was that if you provide enough hiding spots they won't dig so we bought used & dirt cheap wooden dog houses for her. That seems to have worked, she's never dug a burrow but she did dig some nests & laid eggs this year.
When she dug the nests she began with her front feet, then as she got down to a point where she was close to where she wanted to be, she began to use her back feet as shovels.
Very carefully digging the ground with her back feet.
It could be nests your tortoise is trying to dig or it could be that she doesn't have enough hiding spots.
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PHRatz