The 6.5 Grendel and 6.8 SPC are decent rounds for what you described of your/her needs.
I believe she would be better off with the 25 WSSM or one of Oly Arms new 300 WSSM uppers. Mike Milli, aka Dtech, can build her a custom 300 WSSM that will rival 30-06 velocities. The problem is the barrel length, it will likely need to be longer than 18 inches, you need to step up to 22 inches of barrel or more to get there, however, this can all be done on the AR15 Platform with no problems at all. Wait time on the 30 WSSM will be a year or more.
Let's go back to the 6.8 for a minute. For a very good all around caliber the 6.8 fits the bill quite nicely. It is designed to obtain high enough velocities using a 16 or 18 inch barrel, there is a some-what decent selection of bullets available and more coming in the next year or so. Brass is easy to get when SSA has it, recoil is very mild and if you put a brake on it, they literally feel like shooting a 22 LR. The 6.8 ammo is available on the shelves at Cabela's and mail order, complete uppers are available from many sources as is barrels and parts. WSSM parts are only available through Oly Arms, Mike MIlli, or Dan Carey and possibly AR15 Performance.
Keep in mind this very simple rule. IF, you or she decides to go with the 6.8SPC you must stay with the latest of the chamber designs and twist rates. There have been some small but necessary changes to the chamber specs and twist rates over the past couple of years that do indeed improve the performance of the 6.8.
What is important is an 11 or 12 twist and what is now known as the SPEC II DMR chamber. I would go here and read before making a purchase......
http://ar15performance.com/Do I think this is the BEST round? Well, no but I do believe it to be a good round when using a short 16 or 18 inch barrel. Performance over the 223 is much improved and the ability to use it effectivly on larger game is without question a good thing. I have two of the 6.8's and really enjoy the extra power in a short rifle.
JUst to touch on the 6.5, I don't have any experience with it so you info will have to come elsewhere, I can say it may be more expensive to shoot and the reports are that it does perform well out to 600 yards for accuracy, but then that is where the 6.5 bullets shine. Out to 300 yards there will likely be little advantage for accuracy between the two and for hunting there will absolutely be no advantage.
Good luck with the decision.
