Troi was for needing long, extended, psychological care for emotional issues. Guinan has shit to do so isn't going to spend an hour once a week listening to some woman trying to get over her lost husband.
As said, Guinan could provide some friendly, one-off, advice to get one on the right path or make a decision but that's a lot different than emotional support and correction that is part of Troi's profession.
As said, Guinan could provide some friendly, one-off, advice to get one on the right path or make a decision but that's a lot different than emotional support and correction that is part of Troi's profession.