My wife and I signed a preliminary sales agreement 5 days ago. I want to withdraw but my wife refuses. Does my withdrawal imply that of my wife?

Yes, if the preliminary sales agreement you signed with your wife designates the two of you as inseparable purchasers, and you are married under the community of property regime, in accordance with the ruling of the French Supreme Court dated September 14, 2017 (N°16-17.856).