If your wife wants to calls just one location always, the cheapes option is to get a couple of Aplio phones.
They go from $30 to $50 dollars each on e-bay.
The dial up version will be the best.
You will need:
1)I dial up access to the internet on each end. AOL does not work. Most $10 dollars a month provider will do.
2) One Aplio phone device on each end.
3) Two single line phones. You could still use the one at home.
The way that the Aplio works, both gateways dial up to the internet at the same time.
When they connect to the server (free service), they exchange I.P. addreeses and initiate a I.P. to I.P. sesion on their own.
Talk as long as you want and pay only internet acccess on both ends.
If you need information about aplios, you could write to firstname.lastname@example.org.
I saved a bundle with those until I moved to a Quintum gateway.