This is still an argued issue because USCIS haven't had a clear answer. But, if the F-1 holder maintains the term and conditions of F-1 status (such as full time student, less than 20 hr/per week on campus employment etc.) he (or she) is till in F-1 after filing I-485 based on the information from NGLU 2003-10-a SEVIS conference call (please refer my previous article for detail). I assume that your wife is fine it she doesn't use EAD anf enrolls enough credits.
Only for your reference.