The GM can give as many or as few as they like, minimum zero.
The guidelines are in the Basic Set (Campaigns book) on pages 498-499. Above all, the GM is encouraged to figure out for him/herself how many points to award and what criteria to use, and to take into account various things in deciding what the range should be, such as the campaign type (e.g. where on the scale from realistic limited abilities to superheroes?) and how long the campaign is expected to run and so on.
The generic guideline is to award 0 to 5 points to each character per session or adventure, usually 2 or 3. There are no guidelines suggesting giving more points for a single player, but presumably they'll be pretty well engaged, so it may tend to average more.
With the benefit of decades of GURPS play and GMing behind me, I would suggest:
If you're just introducing a new player to the game and aren't planning an extended campaign, and you feel like giving them more points than suggested, go ahead.
If you do hope this will be a long campaign using this character, you might want to consider how many sessions you might play and how powerful you think a character should get after how long, and plan a curve of average awards that matches that. Otherwise you can end up with super-heroes which you didn't mean to play. But you can also start off with fairly fast development and then slow it down to diminishing returns as they become more experienced.