Well, the idea of a battle in ToA seems to be that the enemy decides when to stop the battle. Some enemies, like Brigand, would fight until they're too beaten to move, but others, like Dark Knight, will just decide it's enough trouble for them and just admit defeat.
Wereslut seems to be very strong, but simply not interested in fighting for long. You know, animals almost never fight at their full power, because it is a waste of energy.
So the game wants to say that this beast is so magically strong that if she really wants to catch you and force, she will. But she isn't interested if you're not a strong mate, or an experienced one, or look like a proper wolf. Which makes her one of the easiest to fend off. Plus you're a bit off guard.