As the mare gets close to the general store she weighs her options. If the fishponies are looking for the cart now then that's just another pair of eyes on her along with the monster guards when she tries to move her cargo. The other problem being of course, that she has to move back in the direction of the smokehouse, which is very near the beach.
But waiting would waste time, and she would have to find a place to hide both the cart and herself while they search. If they find the cart she is back at square one. Other than that, they'll know she is out of Antoine's room, and that she wants a cart for some reason.