She doesn't look that old ;)
This makes a great deal of sense, except that you might want to include interaction with other lonely elderly people. That would probably be easier than making the bot smart enough to talk anyway.
A project related to this, from CMU's Human-Computer Interaction Institute by Abigail Travis, can be found here. Scroll down to "Interface, interaction, and concept design for BingBot, a game-playing robot for the elderly."