Mom could be anything, honestly. I've gotten litters of kittens - one will look pure siamese, and the others will be black and calico. I don't get how they could know dad was pitty, but not what mom was. Doesn't mom carry the pups?? hmmm
And...I do think it was a poor choice, on the part of the shelter, to list a pit mix as a breed other than pit. That's setting some up to fail/be returned - IME.
That said... she could be a dobie mix, you'll get a better guess once she gets a bit bigger. I can see the pit, and who knowssss what else!!