I'm with ridge runer. A .223 is plenty on whitetail. Specially if you only take broadside shots through the vitals. A deer WILL NOT survive that shot, he will not go far.
Why do people insist on marginfor error, that is just plain stupid. With that theory no one should bow hunt, because there is absolutely no margin for error using a bow. If you dont hit the vitals you missed. A gut shot deer is not the way to measure a rifles performance, or an arrow, but is a way to measure the performance of the person behind the gun or bow. Just get a .223, use good bullets , take only broadside shots, and she'll be happy, and they'll be venison on the table.