Ruby was relieved. As expected of a god-like Fate, of course he was immune to that girl's charm magic. This is the ability that she used to gain the position of the saintess of The Church of Divine Promises.
This ability, and the fact that Mary Jane Dawson was willing to carry out any orders she was given by the church, established a relationship of mutual benefits between them.
Fate smiled at how Ruby looked visibly relieved. As the properly prepared and paranoid individual that he is, Fate went through relentless psychological training in his last life to resist the temptations of women. He gave up women for a whole week one time. This was the hardest thing Fate had ever done in his life.
