Legal analysis: you can apply to the court for handwriting identification, and designate relevant institutions to make an expert conclusion to determine the authenticity of the matter. An IOU is an important document for borrowing money. If "she" copied your signature and forged an iou of100000 yuan, she will take you to court, and the court will follow your request. The expenses incurred shall be paid in advance by you, and finally borne by the court that ruled against the case.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 667 A loan contract is a contract in which the borrower borrows money from the lender, repays the loan at maturity and pays interest.

Article 668 A loan contract shall be in written form, unless otherwise agreed between natural persons.

The contents of a loan contract generally include terms such as loan type, currency, purpose, amount, interest rate, term and repayment method.

Article 669 When concluding a loan contract, the borrower shall, at the request of the lender, provide the true information about the business activities and financial status related to the loan.