A relatively easy way to eliminate stress as the cause is to go on a nice (ideally, 9 day) vacation together in a very laid back place. You don't want to be going on a "high activity" vacation (every day is booked with activities, site seeing, museums, etc.). What you want is a place where you're days are going to go like this: wake up whenever you want, breakfast, wander down to beach or pool ... maybe a bike ride ... back to room ... shower ... lunch ... back to the beach or pool or sprawl in bed and watch a movie or read a book ... take about 1/2 hour to consider where to eat dinner ... rinse and repeat.
If her libido hasn't kicked up to a more pleasant level by about day 5, then y'all can rule out stress and she needs to make an appointment with an endocrinologist who has a subspeciality in women's sexual health. Don't go to a gynocologist for this, get an endo.
But try to eliminate stress as a cause first. If it is stress, then she needs to develop coping skills or, frankly, get a new job, short and sweet, because that kind of stress eventually does a lot more than suck away your sex drive, it sucks away your life and health.