Add olive oil to the Instant Pot. Turn on Instant Pot to SAUTE. Once the Instant Pot is hot, add the chicken and sauté until cooked through. Turn the Instant Pot off.
Add the chicken broth, milk, buffalo sauce, pasta, and cream cheese in that order. Do not stir. Place lid on Instant Pot. Close the pressure valve. PRESSURE on high for 5 minutes. Then QUICK RELEASE.
When pressure is released, stir ingredients together. Add shredded cheese and stir until combined. If you choose, top with crumbled blue cheese and green onions.