Separation Agreement and date signed

My wife signed a separation agreement in Sept of 2012; she moved out in Dec 2012 or Jan 2013. I filed for divorce in Sept 2014. Wife is now contesting separation agreement and using date signed to consider it invalid. An attorney created and we both signed prior to her leaving. It was done prior so she could purchase a house; the bank wanted her to have some type of agreement in place. Does she have a valid argument?

It is rare to have a situation where the separation agreement is signed and the parties are still living together - technically separation doesn’t begin until you are living apart from each other. Does the agreement reflect that you will separate within a certain time-frame of the execution of the agreement?