How can I guarantee a cutting becomes a hermaphrod...

I can't really tell from the photos if your plant is a Hermie. The only thing you can do at this point is just keep growing her way past harvest to see if she will Hermie. But you are better off taking that pollen and pollinating another clone that has just entered flower. She might not be in good enough health to produce good seeds that late in her cycle. Colloidal silver is a good option to force pollen but it has to be started at the first sign of flower.