Rider
As soon as Sakura arrived and spoke in apology, Rider's fellow servant immediately fell to her knees, apologising profusely for the inconvinience they had caused. Rider had to stiffle her laughter at the display, and at Sakura's obviously-shocked response. After all, Sakura had neither demanded nor received such submissive acts from her servants before. In fact, it reminded her more of the sort of thing Shinji had made her do in the brief time she was under his tyrannical control.
As Rider had expected she would, Sakura quickly corrected the servant, informing her that she did not want her servants to act like, well, servants. Jeanne, though, was still adament that the whole situation was her fault, blaming herself for the inconvinience she had caused with her arrival. Again, Rider was surprised by the level of submissiveness and self-flagellation being shown by the servant, who evidentially felt genuinely bad about the inconvinence they had caused.
Still, despite how unusual it was, Rider did not blame the servant one bit. After all, in her own way, Rider was just as submissive to Sakura's needs and wants as Jeanne was. She simply went about it in a different way, recognising that Sakura was a kind person who wanted those around her to be happy in their own right. In fact, the obvious concern for Sakura's welfare that Jeanne was showing demonstrated to Rider that she could be trusted.
In response to Jeanne's comment, Sakura responded as Rider would have expected, making it clear that she wanted the new servant to be a friend like Rider, not merely a protector like Vanguard had been until he molested Rin. In fact, it was clear that Sakura was actually enthusiastic about buying the girl clothes, in much the same way as she had been for Rider earlier.
Then, wanting to back up Sakura's words with her own, Rider spoke, a smile on her face.
"Jeanne, Sakura is a wonderful and kind master who treats her servants with respect. In fact, she is like family to me. She has always been happy to help me when I needed help and, in turn, I protect her with everything I have", she added.