The Arbiter obviously wanted to talk with her friend first to understand what was happening and why she was doing something like this. But before doing that, there was something else that she needed to do.
And that most important task was to make sure that the will of the universe was not hurting anymore. The will was something akin to mother for the Arbiter, so obviously preventing her from getting hurt was her main objective.
With that in mind, Arbiter tried to neutralize her friend first. She still did not want to hurt her, so this was the only option available.
But the Sarie from that exact time was incredibly powerful. And even though she was unable to dominate the Arbiter easily like the previous supremes, it was clear that the Arbiter would definitely not be able to take her down any time soon. And while time was passing by, the boundary of the world was breaking down more and more.
