6mm Remington is a hard one to pass over. I also really like the 25-06 as several have stated in addition to my vote for checking it out. If you are having it built or a rebarrel job, a 6.5-06 might be something to consider if you handload!
I personally would stay away from brakes. With one of the light kicking calibers you are looking towards, a brake is not necessary and the noise is horrible! I would just make sure that the rifle fits your wife and has a nice recoil pad. When she practices, especially at first, have her put soft plugs under the ear muffs so she has double protection. In a lot of shooters, the percieved recoil is somewhat enhightened by the noise when the rifle goes off. Heck I do this myself. It doesn't hurt to double your protection. We are only given one set of ears!
6mm Remington
25-06
6.5-06