I mean accounting for someone as wealthy as Rih isn't simple. Even if she was looking at her bank account numbers, I'm sure it would be hard to actually sort between her actual income, non-liquid assets (houses, jewelry, bonds, stocks, investments, etc.), and spending money. Especially when her money situation basically depends on the success of her music and endorsements, which can end at any time. We really have no idea how involved she was and how much she was paying attention.
Ultimately it is up to an accountant to make sure their client is making wise financial decisions. If her accountant was purposefully misleading her than he is in the wrong, plain and simple
