My guest arrives today and she only paid for 1 not 2 guest. Would charging for the additional person be too late? Would it be worth it since it is her daughter?
Yes, charge. Go to Dashboard, Your Reservations, pick that one, on right side pick Change or Alter Reservation & look at the many drop down menus. You can change listing or price or dates or number of people.
@Lajewell0 Your listing doesn't say anything about an additional charge for the second guest. The fact that the guest neglected to change the setting from 1 to 2 when booking was probably an oversight on her part, but it wouldn't have made any difference to the rate that AirBnB showed or charged.