。
She is merciful.
Literal
She [topic-は] mercy-deep.
慈悲深い ('merciful, compassionate') is a compound i-adjective — 慈悲 ('mercy, compassion') + 深い ('deep'). The ~深い suffix is productive for forming character-trait adjectives: 用心深い ('cautious'), 興味深い ('interesting / deeply intriguing'), 注意深い ('attentive'), 疑い深い ('suspicious, doubting'). The metaphor — depth of a quality as its strength — translates surprisingly well to English ('deeply X'). 慈悲 itself comes loaded with Buddhist resonance: 慈 ('compassion to give joy') and 悲 ('compassion to remove suffering') are foundational Buddhist virtues.