。
She's always defending her beliefs.
Literal
She [topic-は] always self [possessive-の] beliefs [object-を] is-defending.
弁護する (べんごする, 'to defend, to advocate for') is a formal verb often used in legal contexts (弁護士 = 'lawyer') but works for defending ideas too. 信念 (しんねん, 'beliefs, convictions') refers to deeply held principles. The ~ている form shows this is a persistent behavior.