Double Taxation (Paris)

My wife is a US citizen living and working in France and she has a 10-year carte de sejour. She came from the US in Protected content pays taxes to the IRS but her local French tax office also wants to tax her and they don't understand about the international agreement on taxation between France and the USA, preventing double taxation. The tax office recently removed 2/3 of her salary at source on two consecutive months leaving her in a desperate state to pay bills. She has hired a French lawyer and accountant to try and help but they are both useless. Can you please recommend someone to help who knows both US and French tax systems and who can represent my wife's legitimate objections to paying double tax, back-double-tax and fines for non-payment of double-tax? The tax office staff clearly know nothing and make mistakes but are happy to take actions that cause financial chaos in our lives.