R.S.
I use AF Crossroads (open to all DEERS eligible folks). http://www.afcrossroads.com
That said, tell her Wal-Mart is like the Werkauf or a big Real. She may feel comfortable taking trips towards Newbraunfels area (a good 4 hour drive from Killeen) as we have a large German population there and the language is still spoken, just in a more old-time fashion.
I'm sure she won't be the only German wife, or European wife. I know it can be shell-shock to move around Europe, but just jump in! Chances are she knows more about the US than she needs (American Idol, etc). Killeen can be really, really hot and dry in the summers, so that's probably going to be her biggest adjustment.
If she has time, before the move, she can order a tourist guide to my state by going to http://www.traveltex.com/ . The site is available in German if she'd feel more comfortable in her native tongue.