Sakura and Shirou
The two of them listened to the girl's explanation with interest. It seemed like she was some kind of spiritual figure, a little like Rider had been in life, with the personality to match. Since they were allies, they saw no reason for her to lie, so they were happy to agree to her wish.
"It's fine, we don't need you to prove yourself, you have no reason to lie", Sakura said with a smile. "And you're right, I don't think rushing in and attacking this woman with brute force is likely to work. Fortunately, though, Senpai is good at sniping. And Rider is good at skirmishing, too, although she can hit very hard if she needs to."