Swivelling around, naturally, Sophie couldn't see their pursuer.
The tunnel was too full of twists and turns for that convenience. Further, she didn't even bother to try and sense their magic energy, as that was also doubtful to bear fruit.
All she could do was rely on Anders' sensing, accomplished through contact with his fog.
Although, now that their pursuer had broken through that illusory barrier, and therefore broken contact, it would become more and more difficult to estimate how far away their position was, until they were already too close.
Without the distorted reality of the fog disrupting them, their speed would only increase, and fast, and that wasn't even to mention the fact that the crystal golems between them likely wouldn't have respawned yet.