。
She poured milk into the bowl.
Literal
She [topic-は] bowl's inside [into-に] milk [object-を] poured.
ボール here is the alternate spelling of ボウル ('bowl') — pouring milk into a 'ball' would be nonsense, so context disambiguates. Both ボール (ball) and ボール (bowl) coexist as loanwords from English with distinct senses; ボウル is the more common spelling for 'bowl' precisely to avoid this overlap. の中に literally 'into the inside of' is the standard way to mark 'into' for containers. 注ぐ ('to pour') is a delicate verb, often used for liquids and the careful focus of attention (心を注ぐ 'pour one's heart in').