I've been in the Army for seven years now. If you want a specific location you need her contract to say "guaranteed station of choice" on it, or you won't get it. There is a "wish list" of stations that everybody gets to make, however, if your contract does not specifically say "guaranteed station of choice" then there is no legal obligation for you to get any station on your list.
Her job selection will be based upon both her asvab score, (specifically the "GT" score) and the needs of the army at the time of her enlistment. If she scores above 110 on the GT then she can do any job in the army, and should be able to get any job she wants. If something she wants is not available, then she should walk out. They will call her back, I promise.
Linguists, communications specialists, and other jobs with specialized skills give much higher bonuses than other jobs. In general, the longer the AIT is, the more of a bonus you will receive.
Keep in mind that all enlistments are for 8 years, no matter what you sign up for. For example, I originally signed up for 4 years, which means I served 4 years active, and 4 years inactive. During your inactive years you can still be deployed, you just don't actually work for the army full time.
