Heat the olive oil in a soup pot, add the onion, carrots, and celery, and cook for about 5 minutes until slightly softened.
Stir in the garlic, then add the chicken breast, broth, thyme, salt, and black pepper.
Bring the soup to a boil, reduce the heat, and simmer for 12 to 15 minutes until the chicken is fully cooked.
Remove the chicken from the pot, shred it with two forks, and set it aside briefly.
Add the orzo to the broth and cook according to its package directions, stirring occasionally to prevent sticking.
Return the shredded chicken to the pot, add the spinach, and cook for another 2 minutes until the leaves wilt.
Stir in the fresh lemon juice and parsley, then taste and adjust the seasoning before serving.
