I didn't see it answered but am assuming that both your home office & MIL's computer are 802.11n, obviously if the computers are B/G there is no MIMO distance improvement.

On the other front most Linksys n routers can be re-flashed with dd-wrt. dd-wrt will allow you to crank up the output power above the stock firmware. Obviously the more you crank it up the more heat is produced by the finals which can shorten life. Note that this does nothing for the return channel from the computer to the AP, but if the AP transmitter strength is the weakest link it could give you the boost you need.