Tbh, Ava (so far) comes across as the main character in the same way Ashley comes across as the main character of RE4. Having tuned in for the character that slots into the "survival horror main character" archetype, it can become a little tiring to keep fixating so much on the babysittee, especially when the last chapter appeared to wrap up the "corruption" angle for the villain to shift their attention to someone else from.
In four episodes, Sarah has had two scenes. There comes across a minor feeling of a very, very, very heavy bias towards one character over the other.