Some robos will pace back and forth when they're stressed out. If you've just gotten her, she might not have completely settled in her cage yet, so it's likely that she will stop pacing after a few days. My Smores paced occasionally the first 2 days when she first came home with me, but that behavior disappeared quickly once she stops being nervous and got to know her environment better.
However, persistent pacing (for hours and days) is a neurological problem so keep an eye on her. 45 minutes of continuous pacing does seem like a long time, so when she's resting, see if you can break up the running space like putting furniture or toys in the long paths. If the pacing is neurological, they will run back and forth even in tiny stretch of space. Otherwise, this will help introduce other behaviors such as climbing or investigating new things and hopefully the pacing will stop.