Something to consider:

It doesn't matter what cartridge we all think is the best. If your wife is recoil sensitive and based on you saying that if the 308 has more recoil that the 30-30 that will be a problem, then i'd say she is.
The 270 may be the best deer cartridge around (example) but if she's gonna flinch when shooting it then it's useless.
Not only does she need to be able to shoot it without flinching, i'm sure you would want her to be able to comfortably shoot it at the range.


So we can tell you that the 7mm-08, 308,270, 25-06 is the best but if all she can handle comfortably and shoot accurately is a 243, and that cartridge is adequate for deer, then that's what you need to do