。
She's my girlfriend.
Literal
She [topic-は] my lover is.
恋人 (literally 'love-person') is the standard Japanese term for a romantic partner — gender-neutral, covering 'boyfriend / girlfriend / sweetheart / lover.' Distinct from 彼女 (which can mean 'she' or 'girlfriend' depending on context, sometimes ambiguously) and 彼氏 ('boyfriend'). The lack of grammatical gender on 恋人 makes it the most neutral choice when sex isn't relevant or when the speaker prefers not to mark it.