Use the Southwest hotel booking site and look for hotels offering "Rapid Rewards points plus" rates.
For example, if she were to stay a week in the Treasure Island hotel in Vegas in mid-October ($1,100), she would earn 27,000 points for that stay, not including the points earned on her credit card.
She could plan a staycation in a city near her if travel to a more remote location is not feasible.
Note, however, those points may take up to 8 weeks to post on her account.
I have never done this myself, but I am 98% sure that these bonus points qualify for the companion pass. Others posters can confirm or correct this.

And I also underscore the recommendations above -- will she really use the companion pass enough to justify its cost?