Depending on how far along she is if she is confirmed bred, I would not be too concerned being she is only a week from 15 months. My last heat wave heifer was bred and calved to the simmi bull Built Right at 24 months old when she gave birth without any problem, gave me a great heifer calf this spring that I'm going to keep and put in my herd. I know I-80 is considered an easy calving clubby bull but being a HW, I would probably used a non clubby bull and used I-80 on her 2nd calf, that's just me. But watch her close come calving time and be prepared to intervine. If your into the clubby breeding, you will run into calving problems, it comes with the business. I don't try to create train wrecks, it just happens sometimes.