So thinking ahead a little, this is going to have consequences for the ongoing mess with Rin. Ayako is Rin's only real close friend and prior to the grail war was someone she thought of as an anchor for her normal life as a student. The fact that she's now become involved with the grail war and is actively placing herself in danger to help Shirou is going to further isolate Rin and drive her into a corner. Rin may very reasonably feel like Shirou with his two servants and his countless allies and his talk about being a hero is taking all of the people she cares about away from her and leaving her alone with nothing.
On the other hand Ayako has a strong existing reason to care about Rin's wellbeing and unlike Sakura she's not shy about what she wants. As Rin's friend and a non-master who's not fighting for the grail she's also in a better position to negotiate with her and mediate the conflict than Shirou who's currently Rin's number one enemy. Hopefully in the long term she can help fix things
