The certificate of title is in the name of both of you and your wife. Since you are married, she cannot sell it without you also signing the deed of sale. That's the law.

But of course signatures can be falsified. And with unscrupulous notaries who don't care to check whether the signature appearing on the document belongs to the real person, then it's possible that the property can be sold.
There's really no way to guard against this. The falsification might be discovered too late.

To address this, the original owner's duplicate of the certificate of title must be kept in a secure place. The register of deeds will not process a deed of sale if the original owner's duplicate of the certificate of title is not surrendered to them for cancellation for the issuance of a new certificate in the name of the buyer.

Still it's not fool proof because even if the owner's duplicate is in a secure location, someone can still report the document as missing and petition the court for the issuance of another owner's duplicate of title and use that new owner's duplicate to transact the property.

We just have to rely on the good faith of individuals. A person who wants to defraud another will do all that he can to achieve his purpose. That's why there are lawyers.