Once that it was clear the Resistance was keeping tabs on her somewhat, Hermione avoided all forms of Muggle transportation. It was much more difficult to follow someone on foot without making it obvious. Magic was always theoretically possible, but if the Resistance was trying to avoid detection from the regime in charge, they would have to remain as Muggle-like as possible. Unregistered wands could still be traced because the wand itself wasn't what mattered. Just like the underage witches and wizards of old, the Trace was on the actual person. To try to avoid those she didn't wish to see, she kept walking.