The increase in temperature surprised Su. She had not expected that she would feel it at all. Especially since she had changed armors to a more fire resistant armor prepared for her. It was just a smart method to keep her prepared and also mindful of what each armor felt like when she wore it.
The comfort of her in each new armor would be important while fighting. If she was not comfortable then she might make a mistake. Or if there was an issue with an armor not moving properly with her body, she could find herself being harmed when trying to defend. At the worst case, she could be too slow to protect someone.
Her fire mana resistance was very high. Naturally, she should have been able to make sure that her body resisted the heat. But even with this fire resistant armor, the heat was wearing away at her more than expected.