Yes, anyone may pay your fine.
Try to absorb all of the moisture by blotting with paper towels. Even if it is a small spill, it is important that the book receive treatment as soon as possible in order to prevent mold growth, page blocking (pages sticking together permanently), and warping. If you can't return the book to the library immediately, stand the book up and fan out the pages so that it can air dry. Bring it to the Willis Library Services Desk as soon as possible; do not put it in the book drop. Do not seal it in a plastic bag, as this can encourage mold growth. You may be charged a fine for damaging the book, but if you bring it to the Library as soon as possible, the Preservation Unit can minimize the damage.