Why does a Cat's TAIL poof all out?

When i talk to my cat or make funny noises she goes all rangy..she rubs up against anything bumps her head on anything and rolls around...And all im doin is talkin to her. Shes also 3 years old..Any input??....Just wondering. Her tail goes tot he size of a ratcoons tail....is always poofs out when i talk to her. or make funny noices