So, to summarize this thread, it appears you have a few options:
1. Add her to the roomette reservation. Total cost: $139 each way for her railfare, due when you pick her tickets up (or possibly paid over the phone; your employer should not have to pay for this).
2. Book her a revenue seat in coach and link her record to yours so she can enjoy sleeper benefits. Total cost: dependent on fare buckets, but $139 up to $226 (and possibly higher) each way. Access to sleeper benefits not guaranteed.
3. Book her an award seat in coach and attempt to link her record to yours so she can enjoy sleeper benefits. Total cost: 16,000 AGR points (a relatively low redemption rate of 1.8-2.8 cents per point, depending on fare bucket). Access to sleeper benefits unlikely--you might end up spending a few hundred dollars on just her meals.
4. Cancel your revenue sleeper ticket and book a sleeper award. Ethical solution: negotiate with your company to give you what they were going to pay in cash. Unethical solution: collect the balance of your ticket as a voucher good for future rail travel; the company should never know. Total cost: 40,000 AGR points (you can use 20,000 of your wife's for the way there and 20,000 of yours for the return, if you have that many; a relatively low redemption rate of about 2.5 cents per point, depending on fare bucket, but the only real solution if you don't want to lay out the $278 round-trip for her).
Out of options #1 and #2, there is absolutely no reason to go with #2. #1 does exactly what you want and costs either the same or less. #2 is only a possibility and will cost at least the same and likely more. #3 and #4 are the only ways to do this without spending real money (if that's what you want). Neither is ideal, since it is possible to get a lot more value from your points on other awards, but #3 isn't a reasonable solution if you want to share the trip with your wife--unless you can get Amtrak to bend its policies and allow her to join you. If you arrange it right, #4 could actually put cash in your pocket (or at least in a voucher for future rail travel) but takes the most number of points, which you may not have. (You could have the company pay for one way and use points for the roomette on the return or vice versa.)
Hope this helps...