[Her first instinct is always to walk away, if possible, before the other person can notice her-- and she starts to take a few steps back when she sees Arthur. But it's such an open space, she's already too close to him: there's no way she can be quick and stealthy enough to get away before he notices her.
And that would be kind of awkward. Him looking up to see her skulking away in the other direction. So, hi.]