Prince Cyrus already left to march towards Gazelle Kingdom with his army after assuring Alice that he will be fine alone. After all, he knew himself how risky this war could be.
Letting Alice come with him and see his worst state would possibly not be in his books either. Moreover, the thought and how Kian had described his powers could also overpower his brain, still didn't fit inside his heart much tonight.
Alice didn't wish to let Cyrus leave alone but she had no other options left in her hand either. It was a do or die situation that they both were facing currently. Also, Cyrus had no such wish to harm her. Her father had strictly warned him about the consequences of this war. Even though Alice had powers which were better than anyone else, either a normal vampire or a human, she was still the precious princess of King Vilas.