Why did she let the cat in?

How did the girl detective let the cat inside.

The door was unlocked because her partner suggested the doctor keep it unlocked so they could get in easier.


How did she know that the Dr. Girl had a cat?

Dr. Dalton told Turner she had a cat. We have to assume he told his partner.


Why would you let some random animal into someones house

True, the cat could have been the neighbor's but we have to assume Dr. Dalton gave a description of the cat also. Or maybe the female detective is just really really good :)