Keeping my fingers crossed for you, Molly and Rory that your new girl settles down as she gets used to you.
I got a rescue collie x gsd from the RSPCA once; got him home and he ran right around the bungalow (all around the outside) then did it again ... and again ... and again ... I think he might still be doing it but then one of the cats appeared so he diverted to chase it under the car... It wasn't looking good, frankly. Then we couldn't leave him on his own (he had another dog and two cats for company) as he had seperation anxiety... A few months on and he was the loveliest, lovingest, happiest, most laid back dog you could ever wish to meet, an absolute pleasure to own.