Turn instant pot on saute mode and saute onion with oil for about 3 minutes, add garlic and saute for 2 more minutes.
Hit cancel and add chicken and add 1 cup broth, set to pressure cook for 11 minutes and cook chicken. Turn off instant pot remove chicken to shred chicken thoroughly.
Return chicken to instant pot and add additional 4 cups of broth, set to sauté mode and bring to a boil.
Add orzo to broth and chicken.
In a separate bowl whisk together eggs, the juice of 1 lemon, and about 2 tsp lemon zest.
*Slowly* whisk in about 5 tablespoons of heated broth from instant pot to egg mixture to prevent the eggs from cooking too quickly.
Stir egg, lemon, and broth mixture into soup and turn off sauté mode.
Add in spinach allowing it to wilt.
Serve with fresh pepper and salt.