Susan my experience tells me always cover you back
. I had a similar experience many moons ago for a young lady that was a candidate for Miss US Virgin Islands. When I did the pictures her mom signed my model release. When she won the contest the mother call me to change the release I told her sorry to late to cry. I never made any significant amount of money with the young lady pictures other than what she originally paid me for the porfolio. But if the occation would have come for me to makle money out of her pictures I was covered by law. Some people change when they thing they are queens insted of just regular people so cover your back ALWAYS.
I will make the release for the duration of the competition but during and after that you continue to own the rights to the pictures. The contest can use the pictures at no charge until she wins after that they have to pay you every time the pictures is used if you so desire.