。
Whenever she sees my face, she always makes a sour face.
Literal
She [topic-は] my face [object-を] sees [when-と] always sour face [object-を] does.
いやな顔をする ('to make an unpleasant face') is a fixed expression for visibly registering displeasure — wrinkling the nose, frowning, looking annoyed. The temporal-conditional と links the seeing to the reaction: 'whenever / every time.' The repetition of 顔 in 顔を見る ('look at someone's face') and いやな顔をする ('make an unpleasant face') is intentional — the contrast highlights that her reaction is to seeing the speaker, expressed through her own face. Japanese does not avoid this kind of word repetition the way English often does.