Could it be
Time and Again by Shayne Terry?
A single (unmarried) Lois is transported to the past by Dr. Klein to save the world from an asteroid called Shiva. She has to change the past to save Superman from the kryptonite cage, so he can save the world. She wants to also save Clark who died around the same time as Superman. Instead of being transported to the Daily Planet, she ends up in high school and takes that trip to Smallville in the VW. She bounces around in time.
