It's unlikely that the antibiotics had any affect of her eating issues. It sounds like she was definitely having problems eating with her troublesome teeth. Either way, you'll soon know if that is the case after the course of antibiotics is finished. The antibiotics were most probably prescribed to prevent post op infection from the tooth extraction, not for anything related to the spaying. If she was refusing to eat due to GI problems, she probably would have shown other symptoms, aside from just refusing to eat. Hope you continue to do well little pup