、。
She's keeping a disinterested look, but inwardly she seems thrilled.
Literal
She [topic-は] interest [subject-が]-not [like-ような] face [object-を] is-doing [but-が], inwardly [topic-は] very is-pleased [seems-ようだ].
Two contrasting clauses joined by が ('but') paint a classic Japanese pragmatic contrast: 建前 (the public front) versus 本音 (true inner feelings). The first clause builds 関心がない ('lacks interest') into an adjectival modifier with ~ような ('like / appearing like'), then frames it as a worn expression with ~をしている — 'wearing a disinterested-looking face.' The second clause uses 内心 ('inwardly / in one's heart') paired with ~ようだ to deliver inferred inner state: 'I can't see inside her, but my read is...' The contrast between outer mask and inner truth is itself a culturally valued theme; this gap-reading is part of conversational competence in Japan.