It really depends on what type owl you have there. A great horned owl eats rabbits. Rabbits are easily 3 - 5 pounds. I'd keep her close outside at night.   
My husband and I saw a hawk swoop down and grab an adult mallard duck feeding in our backyard one time. That duck was easily the same size as my dogs.     
				__________________  Deb, Reese, Reggie, Frazier, Libby, Sidney, & Bodie      |