She is highly skilled at investing and managing money.
Tips
grammar
Pattern: 精于 + (此/某) 道 = 'expert in this/that field.' 精 means proficient, 于 marks the domain, and 道 means 'way / craft.' Variations include 精于此事 and 精于书法.
register
Slightly literary; common in essays and reviews when introducing someone's specialty. In casual speech 很在行 (hěn zàiháng) or 很专业 (hěn zhuānyè) sound more natural.