There could be several reasons.  1)The trip was a last minute opportunity so she's interested in working if possible  2)Perhaps she really is staying for a week, but has plans with family/friends on the other days.  No sense in mentioning days you aren't interested in working.  3)Maybe the lady has never visited that city before and isn't really sure she'll have many visitors.  Rather than commit to a week and lose a lot of money, its more feasible to commit to a couple of days.  4)Perhaps she is going to visit for a week, but already has regulars in that city and privately notified them of her visit.  Her regulars have reserved most of her time and she has a couple of days remaining to devote to new clients.

~Simone