Legal Question in Civil Litigation in California

Why did you agree to something like that? What did she offer you? Some contracts can not be enforced if there is no payment/consideration for them, as it then is considered just a gift. A divorce is a matter of public record and it is against public policy to allow any agreement to exist that was done to defraud other people. So if she wanted the divorce kept secret so that that she can receive some type of funds she is not otherwise entitled to, the agreement is null [non-existent]. Legally, you can not blackmail her so an agreement to that effect is meaningless.

Without knowing more details, I can not say with assurance what might happen if you do tell someone. Most likely she is not going to know you spoke to anyone nor could she successfully sue you. Why not call her bluff and demand to have a written statement from her as to why the agreement is legally enforceable?